VaxFact.net
Evidence Navigator · Designed for thoughtful parents

If your child skips this vaccine… what actually happens?

Adjust your situation. See the real tradeoffs — disease risk, vaccine benefit, known side effects, and honest uncertainty — side by side.

6Vaccine cards in V1
4+Independent evidence sources
100%Score formulas visible

Educational tool only. Not medical advice. Always discuss vaccination decisions with your child's pediatrician.

Your Family's Scenario

Adjust these once — all vaccine cards update instantly.

Your child's estimated exposure risk
LOW-MODERATEBaseline risk with minor factors
6–12m
Birth1 yr3 yr6 yr9 yr12 yr
92%
Community protection intact

Vaccine overview cards

Each card answers one question fast: what happens if I give this vaccine, and what happens if I skip it? Scores update live as you change your scenario. Uncertainty bands show the confidence range — wider band means more uncertainty.

FavoredHigh evidence confidence

Hepatitis B

44 years in use · 3 doses · Hepatitis B, Liver cirrhosis

Overall Impact for Your ScenarioiCombines disease risk, vaccine effectiveness, and vaccine side effect profile — adjusted for your specific situation. Not a universal recommendation. Higher = vaccine impact is more significant given your context.

In your situation, the disease risk clearly outweighs the vaccine's known side effect profile.

75
Why this score changed ↓
Exposure riskiProbability of encountering this disease given your scenario. Adjusted by your situation inputs.
58–66Confidence: HIGH
Disease harmiSeverity if contracted: hospitalization rate, mortality, chronic complications, quality of life impact.
96–100Confidence: HIGH
Vaccine riskiAdverse event profile — probability × severity for each known event. Low score = strong safety record. Not zero, but very small relative to disease risk.
4–12Confidence: HIGH
Evidence confidenceiQuality of the research: study types, sample sizes, years of post-licensure data, reproducibility. Uncertainty bands on other scores widen when this is lower.
96
Serious adverse events: very low probability

Without vaccine

  • Exposure: ~140 cases per 100k/yr
  • Hospitalization: 15% of infections
  • Mortality: 25 per 100k infected
  • Chronic sequelae: 90%
  • Chronic hepatitis B requires lifelong monitoring and often antiviral medication. Cirrhosis causes fatigue, jaundice, flu…

With vaccine

  • Effectiveness: 99% against severe disease
  • Residual exposure: ~1.4 per 100k/yr
  • Common side effects: local soreness, low-grade fever (self-limiting, 1–3 days)
  • Rare serious events: 2 documented (see full analysis for incidence)
  • Immunity appears lifelong for most vaccinated individuals. Booster not currently recommended for imm…
What some researchers question

Some researchers argue newborn vaccination is unnecessary in low-prevalence settings where maternal testing reliably identifies infected mothers (Mitkus et al.,…

Strongly favoredHigh evidence confidence

DTaP

30 years in use · 5 doses · Diphtheria, Tetanus (Lockjaw)

Overall Impact for Your ScenarioiCombines disease risk, vaccine effectiveness, and vaccine side effect profile — adjusted for your specific situation. Not a universal recommendation. Higher = vaccine impact is more significant given your context.

In your situation, this vaccine likely prevents a high-risk disease with very low known vaccine risk.

87
Why this score changed ↓
Exposure riskiProbability of encountering this disease given your scenario. Adjusted by your situation inputs.
88–96Confidence: HIGH
Disease harmiSeverity if contracted: hospitalization rate, mortality, chronic complications, quality of life impact.
96–100Confidence: HIGH
Vaccine riskiAdverse event profile — probability × severity for each known event. Low score = strong safety record. Not zero, but very small relative to disease risk.
10–18Confidence: HIGH
Evidence confidenceiQuality of the research: study types, sample sizes, years of post-licensure data, reproducibility. Uncertainty bands on other scores widen when this is lower.
90
Adverse event profile: low

Without vaccine

  • Exposure: ~480 cases per 100k/yr
  • Hospitalization: 35% of infections
  • Mortality: 150 per 100k infected
  • Chronic sequelae: 5%
  • Pertussis in infants causes apnea, cyanosis, and convulsions from hypoxia. Survivors may have neurological injury. Tetan…

With vaccine

  • Effectiveness: 95% against severe disease
  • Residual exposure: ~48 per 100k/yr
  • Common side effects: local soreness, low-grade fever (self-limiting, 1–3 days)
  • Rare serious events: 2 documented (see full analysis for incidence)
  • Pertussis immunity wanes more rapidly than diphtheria/tetanus — significant waning by 4–6 years afte…
What some researchers question

Acellular pertussis vaccines, while safer, appear to generate weaker and shorter-lived immunity than whole-cell DTP. Some immunologists argue the switch to acel…

Exposure-dependentHigh evidence confidence

Hib

35 years in use · 4 doses · Hib meningitis, Hib pneumonia

Overall Impact for Your ScenarioiCombines disease risk, vaccine effectiveness, and vaccine side effect profile — adjusted for your specific situation. Not a universal recommendation. Higher = vaccine impact is more significant given your context.

The evidence favors vaccination, though your specific scenario has meaningful effect on the math.

59
Why this score changed ↓
Exposure riskiProbability of encountering this disease given your scenario. Adjusted by your situation inputs.
35–43Confidence: HIGH
Disease harmiSeverity if contracted: hospitalization rate, mortality, chronic complications, quality of life impact.
96–100Confidence: HIGH
Vaccine riskiAdverse event profile — probability × severity for each known event. Low score = strong safety record. Not zero, but very small relative to disease risk.
1–9Confidence: HIGH
Evidence confidenceiQuality of the research: study types, sample sizes, years of post-licensure data, reproducibility. Uncertainty bands on other scores widen when this is lower.
95
Serious adverse events: very low probability

Without vaccine

  • Exposure: ~75 cases per 100k/yr
  • Hospitalization: 100% of infections
  • Mortality: 450 per 100k infected
  • Chronic sequelae: 25%
  • Hib meningitis survivors who escape death often face lifelong hearing loss (requiring hearing aids or cochlear implants)…

With vaccine

  • Effectiveness: 98% against severe disease
  • Residual exposure: ~0.4 per 100k/yr
  • Common side effects: local soreness, low-grade fever (self-limiting, 1–3 days)
  • Rare serious events: 1 documented (see full analysis for incidence)
  • Immunity from conjugate vaccine is long-lasting. No booster required after complete infant series fo…
What some researchers question

Some pediatric immunologists argue that a 3-dose schedule (as used in Finland and UK) is adequate, making the US 4-dose schedule conservative (Eskola et al., 19…

FavoredHigh evidence confidence

PCV (Prevnar)

24 years in use · 4 doses · Pneumococcal meningitis, Pneumococcal pneumonia

Overall Impact for Your ScenarioiCombines disease risk, vaccine effectiveness, and vaccine side effect profile — adjusted for your specific situation. Not a universal recommendation. Higher = vaccine impact is more significant given your context.

In your situation, the disease risk clearly outweighs the vaccine's known side effect profile.

82
Why this score changed ↓
Exposure riskiProbability of encountering this disease given your scenario. Adjusted by your situation inputs.
77–85Confidence: HIGH
Disease harmiSeverity if contracted: hospitalization rate, mortality, chronic complications, quality of life impact.
96–100Confidence: HIGH
Vaccine riskiAdverse event profile — probability × severity for each known event. Low score = strong safety record. Not zero, but very small relative to disease risk.
6–14Confidence: HIGH
Evidence confidenceiQuality of the research: study types, sample sizes, years of post-licensure data, reproducibility. Uncertainty bands on other scores widen when this is lower.
88
Serious adverse events: very low probability

Without vaccine

  • Exposure: ~160 cases per 100k/yr
  • Hospitalization: 100% of infections
  • Mortality: 250 per 100k infected
  • Chronic sequelae: 30%
  • Pneumococcal meningitis survivors face the same grim sequelae as Hib meningitis: hearing loss, cognitive impairment, epi…

With vaccine

  • Effectiveness: 94% against severe disease
  • Residual exposure: ~20 per 100k/yr
  • Common side effects: local soreness, low-grade fever (self-limiting, 1–3 days)
  • Rare serious events: 1 documented (see full analysis for incidence)
  • Long-lasting immunity against vaccine serotypes. PCV13 replaced PCV7 due to serotype replacement — n…
What some researchers question

Epidemiologists have documented serotype replacement — total pneumococcal disease burden has not fallen as dramatically as vaccine-serotype disease because othe…

Strongly favoredHigh evidence confidence

MMR

55 years in use · 2 doses · Measles, Mumps

Overall Impact for Your ScenarioiCombines disease risk, vaccine effectiveness, and vaccine side effect profile — adjusted for your specific situation. Not a universal recommendation. Higher = vaccine impact is more significant given your context.

In your situation, this vaccine likely prevents a high-risk disease with very low known vaccine risk.

96
Why this score changed ↓
Exposure riskiProbability of encountering this disease given your scenario. Adjusted by your situation inputs.
95–100Confidence: HIGH
Disease harmiSeverity if contracted: hospitalization rate, mortality, chronic complications, quality of life impact.
96–100Confidence: HIGH
Vaccine riskiAdverse event profile — probability × severity for each known event. Low score = strong safety record. Not zero, but very small relative to disease risk.
12–20Confidence: HIGH
Evidence confidenceiQuality of the research: study types, sample sizes, years of post-licensure data, reproducibility. Uncertainty bands on other scores widen when this is lower.
97
Adverse event profile: low

Without vaccine

  • Exposure: ~2200 cases per 100k/yr
  • Hospitalization: 25% of infections
  • Mortality: 200 per 100k infected
  • Chronic sequelae: 8%
  • Measles causes 'immune amnesia' — destroying immunity memory cells and increasing vulnerability to other infections for …

With vaccine

  • Effectiveness: 99% against severe disease
  • Residual exposure: ~11 per 100k/yr
  • Common side effects: local soreness, low-grade fever (self-limiting, 1–3 days)
  • Rare serious events: 3 documented (see full analysis for incidence)
  • Two doses provide lifelong immunity for the vast majority. A small percentage (<3%) of vaccinated in…
What some researchers question

The Wakefield (1998) MMR-autism claim has been thoroughly refuted by 30+ large studies and over 1.2 million children. Wakefield lost his medical license for res…

Timing-sensitiveHigh evidence confidence

Rotavirus

19 years in use · 3 doses · Rotavirus gastroenteritis, Severe dehydration

Overall Impact for Your ScenarioiCombines disease risk, vaccine effectiveness, and vaccine side effect profile — adjusted for your specific situation. Not a universal recommendation. Higher = vaccine impact is more significant given your context.

Timing and situation are important here — review your scenario inputs carefully.

54
Why this score changed ↓
Exposure riskiProbability of encountering this disease given your scenario. Adjusted by your situation inputs.
96–100Confidence: HIGH
Disease harmiSeverity if contracted: hospitalization rate, mortality, chronic complications, quality of life impact.
74–82Confidence: HIGH
Vaccine riskiAdverse event profile — probability × severity for each known event. Low score = strong safety record. Not zero, but very small relative to disease risk.
14–22Confidence: HIGH
Evidence confidenceiQuality of the research: study types, sample sizes, years of post-licensure data, reproducibility. Uncertainty bands on other scores widen when this is lower.
85
Adverse event profile: low

Without vaccine

  • Exposure: ~8500 cases per 100k/yr
  • Hospitalization: 2% of infections
  • Mortality: 5 per 100k infected
  • Chronic sequelae: 0.5%
  • Rotavirus gastroenteritis causes profuse watery diarrhea (up to 20 episodes/day), vomiting, fever, and severe dehydratio…

With vaccine

  • Effectiveness: 87% against severe disease
  • Residual exposure: ~1020 per 100k/yr
  • Common side effects: local soreness, low-grade fever (self-limiting, 1–3 days)
  • Rare serious events: 1 documented (see full analysis for incidence)
  • Protection highest in first 2 years of life — the highest-risk period. Immunity wanes but natural bo…
What some researchers question

Some pediatric gastroenterologists argue that in high-income countries with good medical infrastructure (where IV rehydration is readily available), the severit…

Timing-sensitiveHigh evidence confidence

Varicella

30 years in use · 2 doses · Chickenpox (Varicella), Shingles (Zoster) — reduced lifetime risk

Overall Impact for Your ScenarioiCombines disease risk, vaccine effectiveness, and vaccine side effect profile — adjusted for your specific situation. Not a universal recommendation. Higher = vaccine impact is more significant given your context.

Timing and situation are important here — review your scenario inputs carefully.

8
Why this score changed ↓
Exposure riskiProbability of encountering this disease given your scenario. Adjusted by your situation inputs.
63–71Confidence: HIGH
Disease harmiSeverity if contracted: hospitalization rate, mortality, chronic complications, quality of life impact.
47–55Confidence: HIGH
Vaccine riskiAdverse event profile — probability × severity for each known event. Low score = strong safety record. Not zero, but very small relative to disease risk.
6–14Confidence: HIGH
Evidence confidenceiQuality of the research: study types, sample sizes, years of post-licensure data, reproducibility. Uncertainty bands on other scores widen when this is lower.
88
Serious adverse events: very low probability

Without vaccine

  • Exposure: ~9500 cases per 100k/yr
  • Hospitalization: 0.3% of infections
  • Mortality: 1.4 per 100k infected
  • Chronic sequelae: 0.1%
  • Chickenpox causes 5–7 days of significant discomfort, school absence, and parental work disruption. Invasive Group A str…

With vaccine

  • Effectiveness: 98% against severe disease
  • Residual exposure: ~190 per 100k/yr
  • Common side effects: local soreness, low-grade fever (self-limiting, 1–3 days)
  • Rare serious events: 2 documented (see full analysis for incidence)
  • Protection against severe disease is durable. Protection against mild infection wanes somewhat over …
What some researchers question

The UK JCVI twice declined universal vaccination based on modeling showing that reducing circulation of wild-type virus may reduce the natural immune boosting t…

Exposure-dependentHigh evidence confidence

Hepatitis A

30 years in use · 2 doses · Hepatitis A

Overall Impact for Your ScenarioiCombines disease risk, vaccine effectiveness, and vaccine side effect profile — adjusted for your specific situation. Not a universal recommendation. Higher = vaccine impact is more significant given your context.

The evidence favors vaccination, though your specific scenario has meaningful effect on the math.

59
Why this score changed ↓
Exposure riskiProbability of encountering this disease given your scenario. Adjusted by your situation inputs.
35–43Confidence: HIGH
Disease harmiSeverity if contracted: hospitalization rate, mortality, chronic complications, quality of life impact.
96–100Confidence: HIGH
Vaccine riskiAdverse event profile — probability × severity for each known event. Low score = strong safety record. Not zero, but very small relative to disease risk.
1–9Confidence: HIGH
Evidence confidenceiQuality of the research: study types, sample sizes, years of post-licensure data, reproducibility. Uncertainty bands on other scores widen when this is lower.
90
Serious adverse events: very low probability

Without vaccine

  • Exposure: ~75 cases per 100k/yr
  • Hospitalization: 22% of infections
  • Mortality: 2 per 100k infected
  • Chronic sequelae: 0%
  • Jaundice, profound fatigue, nausea, and abdominal pain lasting 2–6 weeks. Most working-age adults miss 2–4 weeks of work…

With vaccine

  • Effectiveness: 99% against severe disease
  • Residual exposure: ~0.4 per 100k/yr
  • Common side effects: local soreness, low-grade fever (self-limiting, 1–3 days)
  • Rare serious events: 1 documented (see full analysis for incidence)
  • Mathematical models project protection lasting at least 25–40 years based on antibody decay rates. B…
What some researchers question

Some health economists and infectious disease physicians argue that universal toddler vaccination is poorly targeted — the disease burden in children is mild, w…

Exposure-dependentHigh evidence confidence

HPV

18 years in use · 2 doses · Cervical cancer, Oropharyngeal cancer

Overall Impact for Your ScenarioiCombines disease risk, vaccine effectiveness, and vaccine side effect profile — adjusted for your specific situation. Not a universal recommendation. Higher = vaccine impact is more significant given your context.

The evidence favors vaccination, though your specific scenario has meaningful effect on the math.

64
Why this score changed ↓
Exposure riskiProbability of encountering this disease given your scenario. Adjusted by your situation inputs.
52–60Confidence: HIGH
Disease harmiSeverity if contracted: hospitalization rate, mortality, chronic complications, quality of life impact.
96–100Confidence: HIGH
Vaccine riskiAdverse event profile — probability × severity for each known event. Low score = strong safety record. Not zero, but very small relative to disease risk.
8–16Confidence: HIGH
Evidence confidenceiQuality of the research: study types, sample sizes, years of post-licensure data, reproducibility. Uncertainty bands on other scores widen when this is lower.
87
Adverse event profile: low

Without vaccine

  • Exposure: ~1400 cases per 100k/yr
  • Hospitalization: 8% of infections
  • Mortality: 430 per 100k infected
  • Chronic sequelae: 1.2%
  • Cervical cancer treatment involves surgery, radiation, and chemotherapy with significant impacts on fertility, sexual fu…

With vaccine

  • Effectiveness: 97% against severe disease
  • Residual exposure: ~140 per 100k/yr
  • Common side effects: local soreness, low-grade fever (self-limiting, 1–3 days)
  • Rare serious events: 2 documented (see full analysis for incidence)
  • Antibody levels remain elevated for 12+ years of follow-up with no evidence of waning protection. Mo…
What some researchers question

Japan's Ministry of Health received thousands of reports of 'complex regional pain syndrome,' POTS, and cognitive symptoms following HPV vaccination, prompting …

Lower urgencyModerate evidence

MenACWY

20 years in use · 2 doses · Meningococcal disease (serogroups A, C, W, Y), Bacterial meningitis

Overall Impact for Your ScenarioiCombines disease risk, vaccine effectiveness, and vaccine side effect profile — adjusted for your specific situation. Not a universal recommendation. Higher = vaccine impact is more significant given your context.

Your current situation shows low exposure risk. Impact depends strongly on scenario factors.

36
Why this score changed ↓
Exposure riskiProbability of encountering this disease given your scenario. Adjusted by your situation inputs.
8–26Confidence: MODERATE
Disease harmiSeverity if contracted: hospitalization rate, mortality, chronic complications, quality of life impact.
91–100Confidence: MODERATE
Vaccine riskiAdverse event profile — probability × severity for each known event. Low score = strong safety record. Not zero, but very small relative to disease risk.
0–17Confidence: MODERATE
Evidence confidenceiQuality of the research: study types, sample sizes, years of post-licensure data, reproducibility. Uncertainty bands on other scores widen when this is lower.
82
Serious adverse events: very low probability

Without vaccine

  • Exposure: ~1.5 cases per 100k/yr
  • Hospitalization: 95% of infections
  • Mortality: 1000 per 100k infected
  • Chronic sequelae: 20%
  • ~10–15% of patients die despite antibiotics. Of survivors, ~20% suffer permanent sequelae: limb loss from tissue death (…

With vaccine

  • Effectiveness: 85% against severe disease
  • Residual exposure: ~0.15 per 100k/yr
  • Common side effects: local soreness, low-grade fever (self-limiting, 1–3 days)
  • Rare serious events: 1 documented (see full analysis for incidence)
  • Antibody levels wane within 3–5 years, which is why a booster at age 16 is recommended for adolescen…
What some researchers question

Health economists have questioned whether universal adolescent MenACWY vaccination is cost-effective given the low absolute incidence of meningococcal disease i…

Lower urgencyEmerging evidence

MenB

10 years in use · 2 doses · Meningococcal disease (serogroup B), Bacterial meningitis

Overall Impact for Your ScenarioiCombines disease risk, vaccine effectiveness, and vaccine side effect profile — adjusted for your specific situation. Not a universal recommendation. Higher = vaccine impact is more significant given your context.

Your current situation shows low exposure risk. Impact depends strongly on scenario factors.

20
Why this score changed ↓
Exposure riskiProbability of encountering this disease given your scenario. Adjusted by your situation inputs.
0–27Confidence: LOW
Disease harmiSeverity if contracted: hospitalization rate, mortality, chronic complications, quality of life impact.
84–100Confidence: LOW
Vaccine riskiAdverse event profile — probability × severity for each known event. Low score = strong safety record. Not zero, but very small relative to disease risk.
0–31Confidence: LOW
Evidence confidenceiQuality of the research: study types, sample sizes, years of post-licensure data, reproducibility. Uncertainty bands on other scores widen when this is lower.
62
Adverse event profile: low

Without vaccine

  • Exposure: ~0.7 cases per 100k/yr
  • Hospitalization: 95% of infections
  • Mortality: 1000 per 100k infected
  • Chronic sequelae: 20%
  • Identical to meningococcal disease generally — potential for death within 24 hours, limb amputation, deafness, and neuro…

With vaccine

  • Effectiveness: 63% against severe disease
  • Residual exposure: ~0.1 per 100k/yr
  • Common side effects: local soreness, low-grade fever (self-limiting, 1–3 days)
  • Rare serious events: 1 documented (see full analysis for incidence)
  • Effectiveness estimates are 63–73% based on post-licensure real-world studies — lower than many vacc…
What some researchers question

The ACIP deliberately chose not to give a Category A (universal) recommendation, instead issuing a Category B recommendation for individual shared decision-maki…

Timing-sensitiveModerate evidence

RSV Protection

2 years in use · 1 doses · Respiratory Syncytial Virus (RSV), RSV bronchiolitis

Overall Impact for Your ScenarioiCombines disease risk, vaccine effectiveness, and vaccine side effect profile — adjusted for your specific situation. Not a universal recommendation. Higher = vaccine impact is more significant given your context.

Timing and situation are important here — review your scenario inputs carefully.

48
Why this score changed ↓
Exposure riskiProbability of encountering this disease given your scenario. Adjusted by your situation inputs.
75–93Confidence: MODERATE
Disease harmiSeverity if contracted: hospitalization rate, mortality, chronic complications, quality of life impact.
73–91Confidence: MODERATE
Vaccine riskiAdverse event profile — probability × severity for each known event. Low score = strong safety record. Not zero, but very small relative to disease risk.
0–17Confidence: MODERATE
Evidence confidenceiQuality of the research: study types, sample sizes, years of post-licensure data, reproducibility. Uncertainty bands on other scores widen when this is lower.
72
Serious adverse events: very low probability

Without vaccine

  • Exposure: ~7800 cases per 100k/yr
  • Hospitalization: 0.5% of infections
  • Mortality: 20 per 100k infected
  • Chronic sequelae: 0.2%
  • Severe RSV bronchiolitis is distressing for both infants and parents — infants struggle to breathe and feed, sometimes r…

With vaccine

  • Effectiveness: 80% against severe disease
  • Residual exposure: ~1560 per 100k/yr
  • Common side effects: local soreness, low-grade fever (self-limiting, 1–3 days)
  • Rare serious events: 1 documented (see full analysis for incidence)
  • Nirsevimab (monoclonal antibody) provides protection for the entire RSV season (approximately 5 mont…
What some researchers question

The FDA approved Abrysvo despite a numerical imbalance in preterm births in the trial (5.7% vs 4.7%), and the FDA's Vaccines and Related Biological Products Adv…

Timing-sensitiveModerate evidence

Influenza

80 years in use · 1 doses · Influenza A, Influenza B

Overall Impact for Your ScenarioiCombines disease risk, vaccine effectiveness, and vaccine side effect profile — adjusted for your specific situation. Not a universal recommendation. Higher = vaccine impact is more significant given your context.

Timing and situation are important here — review your scenario inputs carefully.

24
Why this score changed ↓
Exposure riskiProbability of encountering this disease given your scenario. Adjusted by your situation inputs.
69–87Confidence: MODERATE
Disease harmiSeverity if contracted: hospitalization rate, mortality, chronic complications, quality of life impact.
65–83Confidence: MODERATE
Vaccine riskiAdverse event profile — probability × severity for each known event. Low score = strong safety record. Not zero, but very small relative to disease risk.
0–14Confidence: MODERATE
Evidence confidenceiQuality of the research: study types, sample sizes, years of post-licensure data, reproducibility. Uncertainty bands on other scores widen when this is lower.
75
Serious adverse events: very low probability

Without vaccine

  • Exposure: ~12000 cases per 100k/yr
  • Hospitalization: 1.5% of infections
  • Mortality: 15 per 100k infected
  • Chronic sequelae: 0.1%
  • Severe flu causes 3–7 days of high fever, body aches, profound fatigue, and respiratory symptoms. Hospitalization rates …

With vaccine

  • Effectiveness: 65% against severe disease
  • Residual exposure: ~5000 per 100k/yr
  • Common side effects: local soreness, low-grade fever (self-limiting, 1–3 days)
  • Rare serious events: 2 documented (see full analysis for incidence)
  • Effectiveness varies year to year based on how well the vaccine matches the circulating strains (ran…
What some researchers question

The Cochrane Collaboration's systematic review of influenza vaccine efficacy in healthy adults (Jefferson et al., 2018, 52 trials) found that while NNT (number …

Timing-sensitiveModerate evidence

COVID-19

4 years in use · 1 doses · COVID-19, Long COVID

Overall Impact for Your ScenarioiCombines disease risk, vaccine effectiveness, and vaccine side effect profile — adjusted for your specific situation. Not a universal recommendation. Higher = vaccine impact is more significant given your context.

Timing and situation are important here — review your scenario inputs carefully.

43
Why this score changed ↓
Exposure riskiProbability of encountering this disease given your scenario. Adjusted by your situation inputs.
64–82Confidence: MODERATE
Disease harmiSeverity if contracted: hospitalization rate, mortality, chronic complications, quality of life impact.
91–100Confidence: MODERATE
Vaccine riskiAdverse event profile — probability × severity for each known event. Low score = strong safety record. Not zero, but very small relative to disease risk.
9–27Confidence: MODERATE
Evidence confidenceiQuality of the research: study types, sample sizes, years of post-licensure data, reproducibility. Uncertainty bands on other scores widen when this is lower.
65
Adverse event profile: low

Without vaccine

  • Exposure: ~8000 cases per 100k/yr
  • Hospitalization: 0.6% of infections
  • Mortality: 8 per 100k infected
  • Chronic sequelae: 3%
  • Acute COVID-19 in children: typically mild respiratory illness. Risk groups: infants <1 year, obese children, those with…

With vaccine

  • Effectiveness: 73% against severe disease
  • Residual exposure: ~2400 per 100k/yr
  • Common side effects: local soreness, low-grade fever (self-limiting, 1–3 days)
  • Rare serious events: 2 documented (see full analysis for incidence)
  • Protection against infection wanes significantly within 3–6 months (20–30% by 6 months). Protection …
What some researchers question

Cochrane's review of COVID-19 vaccine studies highlighted methodological issues in some trials; more broadly, the rapid vaccine development and authorization pr…

Timing-sensitiveHigh evidence confidence

Zoster (Shingrix)

7 years in use · 2 doses · Herpes Zoster (Shingles), Postherpetic Neuralgia (PHN)

Overall Impact for Your ScenarioiCombines disease risk, vaccine effectiveness, and vaccine side effect profile — adjusted for your specific situation. Not a universal recommendation. Higher = vaccine impact is more significant given your context.

Timing and situation are important here — review your scenario inputs carefully.

41
Why this score changed ↓
Exposure riskiProbability of encountering this disease given your scenario. Adjusted by your situation inputs.
46–54Confidence: HIGH
Disease harmiSeverity if contracted: hospitalization rate, mortality, chronic complications, quality of life impact.
96–100Confidence: HIGH
Vaccine riskiAdverse event profile — probability × severity for each known event. Low score = strong safety record. Not zero, but very small relative to disease risk.
11–19Confidence: HIGH
Evidence confidenceiQuality of the research: study types, sample sizes, years of post-licensure data, reproducibility. Uncertainty bands on other scores widen when this is lower.
88
Adverse event profile: low

Without vaccine

  • Exposure: ~1000 cases per 100k/yr
  • Hospitalization: 2% of infections
  • Mortality: 3 per 100k infected
  • Chronic sequelae: 15%
  • Shingles rash causes severe burning and stabbing pain. PHN affects 10–15% of patients over 60 and can be completely debi…

With vaccine

  • Effectiveness: 89% against severe disease
  • Residual exposure: ~80 per 100k/yr
  • Common side effects: local soreness, low-grade fever (self-limiting, 1–3 days)
  • Rare serious events: 1 documented (see full analysis for incidence)
  • Shingrix maintains >85% effectiveness through 7 years of follow-up — substantially more durable than…
What some researchers question

Shingrix has the highest rate of grade 3 (severe, activity-limiting) systemic reactions of any approved vaccine — approximately 17% of recipients. While these r…

Lower urgencyModerate evidence

Typhoid

35 years in use · 1 doses · Typhoid fever (Salmonella Typhi), Paratyphoid fever

Overall Impact for Your ScenarioiCombines disease risk, vaccine effectiveness, and vaccine side effect profile — adjusted for your specific situation. Not a universal recommendation. Higher = vaccine impact is more significant given your context.

Your current situation shows low exposure risk. Impact depends strongly on scenario factors.

37
Why this score changed ↓
Exposure riskiProbability of encountering this disease given your scenario. Adjusted by your situation inputs.
13–31Confidence: MODERATE
Disease harmiSeverity if contracted: hospitalization rate, mortality, chronic complications, quality of life impact.
91–100Confidence: MODERATE
Vaccine riskiAdverse event profile — probability × severity for each known event. Low score = strong safety record. Not zero, but very small relative to disease risk.
0–14Confidence: MODERATE
Evidence confidenceiQuality of the research: study types, sample sizes, years of post-licensure data, reproducibility. Uncertainty bands on other scores widen when this is lower.
78
Serious adverse events: very low probability

Without vaccine

  • Exposure: ~350 cases per 100k/yr
  • Hospitalization: 25% of infections
  • Mortality: 150 per 100k infected
  • Chronic sequelae: 1%
  • Typhoid causes 2–4 weeks of debilitating high fever and gastrointestinal illness. Complications include intestinal perfo…

With vaccine

  • Effectiveness: 80% against severe disease
  • Residual exposure: ~88 per 100k/yr
  • Common side effects: local soreness, low-grade fever (self-limiting, 1–3 days)
  • Rare serious events: 1 documented (see full analysis for incidence)
  • Injectable Typhim Vi: ~75% effective for 2–3 years; revaccinate every 2 years for ongoing travel. Or…
What some researchers question

The injectable Vi polysaccharide vaccine provides only T-cell-independent immunity and does not generate immunological memory — meaning it requires revaccinatio…

Lower urgencyModerate evidence

Yellow Fever

85 years in use · 1 doses · Yellow fever

Overall Impact for Your ScenarioiCombines disease risk, vaccine effectiveness, and vaccine side effect profile — adjusted for your specific situation. Not a universal recommendation. Higher = vaccine impact is more significant given your context.

Your current situation shows low exposure risk. Impact depends strongly on scenario factors.

21
Why this score changed ↓
Exposure riskiProbability of encountering this disease given your scenario. Adjusted by your situation inputs.
0–18Confidence: MODERATE
Disease harmiSeverity if contracted: hospitalization rate, mortality, chronic complications, quality of life impact.
91–100Confidence: MODERATE
Vaccine riskiAdverse event profile — probability × severity for each known event. Low score = strong safety record. Not zero, but very small relative to disease risk.
13–31Confidence: MODERATE
Evidence confidenceiQuality of the research: study types, sample sizes, years of post-licensure data, reproducibility. Uncertainty bands on other scores widen when this is lower.
82
Adverse event profile: low

Without vaccine

  • Exposure: ~50 cases per 100k/yr
  • Hospitalization: 15% of infections
  • Mortality: 5000 per 100k infected
  • Chronic sequelae: 0.5%
  • Mild cases: fever, headache, muscle pain — resolves in 3–4 days. Severe cases (15% of initial cases progress): toxic pha…

With vaccine

  • Effectiveness: 99% against severe disease
  • Residual exposure: ~1 per 100k/yr
  • Common side effects: local soreness, low-grade fever (self-limiting, 1–3 days)
  • Rare serious events: 3 documented (see full analysis for incidence)
  • Single dose provides lifelong immunity for the vast majority of recipients. WHO revised its position…
What some researchers question

The risk of YEL-AVD (yellow fever vaccine-associated viscerotropic disease) increases with age — reaching approximately 1–1.8 per 100,000 doses in adults over 6…

Lower urgencyHigh evidence confidence

Rabies

45 years in use · 3 doses · Rabies

Overall Impact for Your ScenarioiCombines disease risk, vaccine effectiveness, and vaccine side effect profile — adjusted for your specific situation. Not a universal recommendation. Higher = vaccine impact is more significant given your context.

Your current situation shows low exposure risk. Impact depends strongly on scenario factors.

33
Why this score changed ↓
Exposure riskiProbability of encountering this disease given your scenario. Adjusted by your situation inputs.
2–10Confidence: HIGH
Disease harmiSeverity if contracted: hospitalization rate, mortality, chronic complications, quality of life impact.
96–100Confidence: HIGH
Vaccine riskiAdverse event profile — probability × severity for each known event. Low score = strong safety record. Not zero, but very small relative to disease risk.
4–12Confidence: HIGH
Evidence confidenceiQuality of the research: study types, sample sizes, years of post-licensure data, reproducibility. Uncertainty bands on other scores widen when this is lower.
85
Serious adverse events: very low probability

Without vaccine

  • Exposure: ~0.01 cases per 100k/yr
  • Hospitalization: 100% of infections
  • Mortality: 99000 per 100k infected
  • Chronic sequelae: 0%
  • Clinical rabies causes encephalitis progressing to paralysis, hydrophobia (fear of water due to painful throat spasms), …

With vaccine

  • Effectiveness: 100% against severe disease
  • Residual exposure: ~0 per 100k/yr
  • Common side effects: local soreness, low-grade fever (self-limiting, 1–3 days)
  • Rare serious events: 1 documented (see full analysis for incidence)
  • Pre-exposure prophylaxis (PrEP): 3-dose series. Provides memory immunity allowing simplified post-ex…
What some researchers question

The 3-dose pre-exposure series costs $500–1,500 out of pocket in many US travel medicine clinics, making pre-exposure prophylaxis inaccessible to lower-income t…

Lower urgencyEmerging evidence

Dengue

8 years in use · 3 doses · Dengue fever, Dengue hemorrhagic fever

Overall Impact for Your ScenarioiCombines disease risk, vaccine effectiveness, and vaccine side effect profile — adjusted for your specific situation. Not a universal recommendation. Higher = vaccine impact is more significant given your context.

Your current situation shows low exposure risk. Impact depends strongly on scenario factors.

6
Why this score changed ↓
Exposure riskiProbability of encountering this disease given your scenario. Adjusted by your situation inputs.
1–33Confidence: LOW
Disease harmiSeverity if contracted: hospitalization rate, mortality, chronic complications, quality of life impact.
84–100Confidence: LOW
Vaccine riskiAdverse event profile — probability × severity for each known event. Low score = strong safety record. Not zero, but very small relative to disease risk.
9–41Confidence: LOW
Evidence confidenceiQuality of the research: study types, sample sizes, years of post-licensure data, reproducibility. Uncertainty bands on other scores widen when this is lower.
58
Adverse event profile: low

Without vaccine

  • Exposure: ~3500 cases per 100k/yr
  • Hospitalization: 5% of infections
  • Mortality: 500 per 100k infected
  • Chronic sequelae: 0.2%
  • Mild dengue: severe flu-like illness with intense joint pain ('breakbone fever') for 5–7 days. Severe dengue: plasma lea…

With vaccine

  • Effectiveness: 62% against severe disease
  • Residual exposure: ~1750 per 100k/yr
  • Common side effects: local soreness, low-grade fever (self-limiting, 1–3 days)
  • Rare serious events: 1 documented (see full analysis for incidence)
  • Dengvaxia: 60% effective overall in seropositive individuals; acts as a 'prime' for seronegative ind…
What some researchers question

The Dengvaxia Philippines disaster is one of the most important vaccine safety events of the 21st century and must be understood by anyone discussing dengue vac…

Lower urgencyHigh evidence confidence

IPV (Polio)

70 years in use · 4 doses · Poliomyelitis, Post-polio syndrome

Overall Impact for Your ScenarioiCombines disease risk, vaccine effectiveness, and vaccine side effect profile — adjusted for your specific situation. Not a universal recommendation. Higher = vaccine impact is more significant given your context.

Your current situation shows low exposure risk. Impact depends strongly on scenario factors.

49
Why this score changed ↓
Exposure riskiProbability of encountering this disease given your scenario. Adjusted by your situation inputs.
18–26Confidence: HIGH
Disease harmiSeverity if contracted: hospitalization rate, mortality, chronic complications, quality of life impact.
96–100Confidence: HIGH
Vaccine riskiAdverse event profile — probability × severity for each known event. Low score = strong safety record. Not zero, but very small relative to disease risk.
0–7Confidence: HIGH
Evidence confidenceiQuality of the research: study types, sample sizes, years of post-licensure data, reproducibility. Uncertainty bands on other scores widen when this is lower.
97
Serious adverse events: very low probability

Without vaccine

  • Exposure: ~800 cases per 100k/yr
  • Hospitalization: 12% of infections
  • Mortality: 50 per 100k infected
  • Chronic sequelae: 35%
  • Paralytic polio: irreversible flaccid paralysis of one or more limbs. Bulbar polio: paralysis of breathing muscles requi…

With vaccine

  • Effectiveness: 99% against severe disease
  • Residual exposure: ~0.2 per 100k/yr
  • Common side effects: local soreness, low-grade fever (self-limiting, 1–3 days)
  • Rare serious events: 1 documented (see full analysis for incidence)
  • Four doses of IPV provide lifelong immunity against paralytic poliomyelitis. Serum antibody titers r…
What some researchers question

The switch from OPV to IPV in high-income countries has created a two-tier global polio vaccination system: high-income countries use IPV (safer, no VDPV risk) …

Timing-sensitiveModerate evidence

Mpox (Monkeypox)

15 years in use · 2 doses · Mpox (Monkeypox), Smallpox (ACAM2000)

Overall Impact for Your ScenarioiCombines disease risk, vaccine effectiveness, and vaccine side effect profile — adjusted for your specific situation. Not a universal recommendation. Higher = vaccine impact is more significant given your context.

Timing and situation are important here — review your scenario inputs carefully.

50
Why this score changed ↓
Exposure riskiProbability of encountering this disease given your scenario. Adjusted by your situation inputs.
25–43Confidence: MODERATE
Disease harmiSeverity if contracted: hospitalization rate, mortality, chronic complications, quality of life impact.
91–100Confidence: MODERATE
Vaccine riskiAdverse event profile — probability × severity for each known event. Low score = strong safety record. Not zero, but very small relative to disease risk.
3–21Confidence: MODERATE
Evidence confidenceiQuality of the research: study types, sample sizes, years of post-licensure data, reproducibility. Uncertainty bands on other scores widen when this is lower.
78
Adverse event profile: low

Without vaccine

  • Exposure: ~85 cases per 100k/yr
  • Hospitalization: 12% of infections
  • Mortality: 1 per 100k infected
  • Chronic sequelae: 8%
  • The rash is intensely painful, especially when lesions appear on the face, genitals, anus, or mouth. Healing takes 2–4 w…

With vaccine

  • Effectiveness: 93% against severe disease
  • Residual exposure: ~7 per 100k/yr
  • Common side effects: local soreness, low-grade fever (self-limiting, 1–3 days)
  • Rare serious events: 1 documented (see full analysis for incidence)
  • JYNNEOS (2-dose subcutaneous series) showed 86% effectiveness in the 2022 outbreak per CDC studies. …
What some researchers question

Some researchers argue the risk-stratified approach (vaccinating only 'at-risk' populations) creates stigma and misses transmission chains in heterosexual netwo…

Lower urgencyModerate evidence

Cholera

30 years in use · 1 doses · Cholera (Vibrio cholerae)

Overall Impact for Your ScenarioiCombines disease risk, vaccine effectiveness, and vaccine side effect profile — adjusted for your specific situation. Not a universal recommendation. Higher = vaccine impact is more significant given your context.

Your current situation shows low exposure risk. Impact depends strongly on scenario factors.

39
Why this score changed ↓
Exposure riskiProbability of encountering this disease given your scenario. Adjusted by your situation inputs.
8–26Confidence: MODERATE
Disease harmiSeverity if contracted: hospitalization rate, mortality, chronic complications, quality of life impact.
91–100Confidence: MODERATE
Vaccine riskiAdverse event profile — probability × severity for each known event. Low score = strong safety record. Not zero, but very small relative to disease risk.
0–15Confidence: MODERATE
Evidence confidenceiQuality of the research: study types, sample sizes, years of post-licensure data, reproducibility. Uncertainty bands on other scores widen when this is lower.
82
Serious adverse events: very low probability

Without vaccine

  • Exposure: ~300 cases per 100k/yr
  • Hospitalization: 20% of infections
  • Mortality: 200 per 100k infected
  • Chronic sequelae: 1%
  • Severe cholera causes extreme dehydration, muscle cramps, sunken eyes, and circulatory collapse. Death can occur within …

With vaccine

  • Effectiveness: 88% against severe disease
  • Residual exposure: ~60 per 100k/yr
  • Common side effects: local soreness, low-grade fever (self-limiting, 1–3 days)
  • Rare serious events: 1 documented (see full analysis for incidence)
  • Protection wanes over 2–3 years. In endemic settings, Shanchol/Euvichol provides ~65% protection for…
What some researchers question

Some global health experts argue that oral cholera vaccine (OCV) campaigns divert resources from water and sanitation infrastructure, which is the only sustaina…

Lower urgencyHigh evidence confidence

Japanese Encephalitis

35 years in use · 2 doses · Japanese Encephalitis

Overall Impact for Your ScenarioiCombines disease risk, vaccine effectiveness, and vaccine side effect profile — adjusted for your specific situation. Not a universal recommendation. Higher = vaccine impact is more significant given your context.

Your current situation shows low exposure risk. Impact depends strongly on scenario factors.

38
Why this score changed ↓
Exposure riskiProbability of encountering this disease given your scenario. Adjusted by your situation inputs.
5–13Confidence: HIGH
Disease harmiSeverity if contracted: hospitalization rate, mortality, chronic complications, quality of life impact.
96–100Confidence: HIGH
Vaccine riskiAdverse event profile — probability × severity for each known event. Low score = strong safety record. Not zero, but very small relative to disease risk.
4–12Confidence: HIGH
Evidence confidenceiQuality of the research: study types, sample sizes, years of post-licensure data, reproducibility. Uncertainty bands on other scores widen when this is lower.
85
Serious adverse events: very low probability

Without vaccine

  • Exposure: ~20 cases per 100k/yr
  • Hospitalization: 100% of infections
  • Mortality: 2500 per 100k infected
  • Chronic sequelae: 40%
  • JE encephalitis causes fever, seizures, altered consciousness, and paralysis. Survivors frequently suffer cognitive impa…

With vaccine

  • Effectiveness: 99% against severe disease
  • Residual exposure: ~0.4 per 100k/yr
  • Common side effects: local soreness, low-grade fever (self-limiting, 1–3 days)
  • Rare serious events: 1 documented (see full analysis for incidence)
  • Two-dose primary series (Ixiaro) provides robust protection. Seroprotection persists for at least 12…
What some researchers question

The original Japanese JE vaccine (mouse-brain derived) carried a small but real risk of hypersensitivity reactions and has been replaced by modern cell-culture …

Exposure-dependentHigh evidence confidence

Tdap (Adult Booster)

20 years in use · 1 doses · Tetanus (Lockjaw), Diphtheria

Overall Impact for Your ScenarioiCombines disease risk, vaccine effectiveness, and vaccine side effect profile — adjusted for your specific situation. Not a universal recommendation. Higher = vaccine impact is more significant given your context.

The evidence favors vaccination, though your specific scenario has meaningful effect on the math.

65
Why this score changed ↓
Exposure riskiProbability of encountering this disease given your scenario. Adjusted by your situation inputs.
58–66Confidence: HIGH
Disease harmiSeverity if contracted: hospitalization rate, mortality, chronic complications, quality of life impact.
96–100Confidence: HIGH
Vaccine riskiAdverse event profile — probability × severity for each known event. Low score = strong safety record. Not zero, but very small relative to disease risk.
4–12Confidence: HIGH
Evidence confidenceiQuality of the research: study types, sample sizes, years of post-licensure data, reproducibility. Uncertainty bands on other scores widen when this is lower.
88
Serious adverse events: very low probability

Without vaccine

  • Exposure: ~200 cases per 100k/yr
  • Hospitalization: 5% of infections
  • Mortality: 15 per 100k infected
  • Chronic sequelae: 3%
  • In adults, pertussis causes the '100-day cough' — weeks of violent coughing fits that can fracture ribs, cause urinary i…

With vaccine

  • Effectiveness: 88% against severe disease
  • Residual exposure: ~60 per 100k/yr
  • Common side effects: local soreness, low-grade fever (self-limiting, 1–3 days)
  • Rare serious events: 2 documented (see full analysis for incidence)
  • Pertussis immunity wanes significantly — protection drops to ~70% within 2–3 years of Tdap and to ne…
What some researchers question

Some researchers argue the current Tdap strategy — vaccinating pregnant women every pregnancy — is an acknowledgment of a fundamental failure of acellular pertu…

How this tool thinks

We use a transparent, multi-source weighting model. No single agency's recommendation drives the output. The goal is visible reasoning, not a predetermined answer.

⚖️
Not pro or anti
This tool has no predetermined conclusion. It computes from data and shows you the math.
🔍
Risk vs consequence
Every score weighs both sides: what the disease does, and what the vaccine does.
🌐
Transparency over authority
CDC is one input. WHO is one input. Studies are one input. No single source dominates.
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Uncertainty is visible
Every score has a confidence range. Lower confidence = wider band. We show what we don't know.
What this tool does NOT do
Does not replace medical advice from your pediatrician. Does not guarantee outcomes for any individual child. Does not use a single authority — CDC, WHO, and peer-reviewed studies are all weighted inputs, not final answers. Does not present certainty where uncertainty exists.
What goes into 'Overall Impact for Your Scenario'?

It is computed from four dimensions: Exposure Risk (how likely your child encounters the disease), Disease Consequence (how severe the disease is), Vaccine Benefit (how much the vaccine reduces that risk), and Vaccine Harm (adverse event probability × severity weight). The formula is fully transparent and visible in our methodology.

Why does the score change when I adjust my scenario?

Scenario modifiers — daycare, travel, local outbreaks, older siblings, immunocompromised household — are multipliers on the Exposure Risk dimension. When your exposure context changes, the effective risk changes, which shifts the Overall Impact score. This is the core design: the tradeoffs depend on your situation, not a population average.

What do the uncertainty bands mean?

Every score has a range (e.g., 'Exposure Risk: 42–58') reflecting the confidence in the underlying data. Wider band = more uncertainty in the evidence base. The 'Evidence Confidence' bar controls band width: low confidence produces wide bands. This is intentional — we show what we don't know.

How is 'Vaccine Risk' measured?

Each known adverse event is weighted by its probability (per 100,000 doses) and severity (mild, moderate, serious, rare-serious). A score of 6 means the modeled harm from the vaccine is extremely low — not zero, but very small relative to the 0–100 scale. We use post-licensure surveillance data from VAERS, VAX-view, and peer-reviewed safety studies.

Where does the 'What some researchers question' section come from?

These are documented concerns from peer-reviewed literature, independent researchers, or credentialed practitioners — not fringe or conspiracy content. They are given equal visual weight to the consensus position because intellectual honesty requires showing the full picture.

HOW THIS TOOL THINKS

Decision philosophy

VaxFact is built on a specific philosophy about how to present medical evidence to parents. Understanding it helps you use the tool well.

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Full methodology documentation

The complete technical methodology — including the scoring algorithm, data sources, evidence hierarchy, scenario modifier weights, and uncertainty band calculations — is documented in the VaxFact Technical Manual. Each vaccine entry includes full source citations, evidence quality ratings, and the reasoning behind every score component.