Hepatitis A Vaccine
Hepatitis A
Hepatitis A virus (HAV) is a self-limiting liver infection. Unlike HepB, it does not cause chronic disease. However, it causes acute liver failure in ~0.5% of cases, with fatality rates rising sharply in adults and those with pre-existing liver disease. Large outbreaks have swept through homeless communities and produce/restaurant supply chains.
Overall Benefit Score
Default scenario · 12-month-old · US community (92% vax rate)
Score for your child →The evidence moderately supports this vaccine for your child's situation. Benefits outweigh risks but some factors in your scenario lower the urgency.
📊 Evidence Scores
Scores computed from peer-reviewed data using VaxFact's evidence model. Based on default scenario (12-month-old, standard US community).
🦠 Disease Burden
Hepatitis A virus (HAV) is a self-limiting liver infection. Unlike HepB, it does not cause chronic disease. However, it causes acute liver failure in ~0.5% of cases, with fatality rates rising sharply in adults and those with pre-existing liver disease. Large outbreaks have swept through homeless communities and produce/restaurant supply chains.
Jaundice, profound fatigue, nausea, and abdominal pain lasting 2–6 weeks. Most working-age adults miss 2–4 weeks of work. A prolonged relapsing form affects ~10–15% and extends illness for months. Full hepatic failure requiring transplant occurs rarely but is devastating.
🛡️ Vaccine Effectiveness
Mathematical models project protection lasting at least 25–40 years based on antibody decay rates. Booster not currently recommended for immunocompetent individuals after primary series. Some immunocompromised patients may need booster.
Breakthrough infections are exceptionally rare — fewer than 1 per 100,000 vaccinated per year in surveillance data.
⚠️ Adverse Events & Side Effects
All probabilities are per 100,000 doses administered, sourced from VAERS, Vaccine Safety Datalink, and post-licensure surveillance studies.
Common Side Effects
Rare Serious Events
📅 Vaccine Schedule
Unvaccinated children through age 18 should receive 2-dose catch-up series. Adults traveling to endemic areas should receive dose 1 at least 2 weeks before departure.
⚖️ Benefits vs. Considerations
✓ Benefits
- 99% effective — among the highest efficacy of any vaccine
- 30 years of post-licensure safety data with an exceptionally clean adverse event profile
- Prevents a miserable weeks-long illness that causes major work/school disruption
- Critical protection for international travel to most of the developing world
- Eliminates disease in communities once herd immunity is achieved — demonstrated in Israel and US states that introduced universal vaccination
- Single dose provides protection within 2 weeks — useful for pre-travel
↕ Considerations
- HepA rarely causes death in children — benefit is largest in adults and those with liver disease
- Requires 2 doses 6 months apart for full protection
- Significant injection site pain (~50% of recipients)
- Not on routine schedule in many high-income countries with low endemic risk
🔬 What Some Researchers Question
These are legitimate scientific debates — not fringe claims. They represent areas of ongoing research or policy disagreement among credentialed experts.
- Some health economists and infectious disease physicians argue that universal toddler vaccination is poorly targeted — the disease burden in children is mild, whereas the vaccine's greatest impact is in adults and those with liver disease. Targeted vaccination of high-risk populations may achieve similar public health outcomes at lower cost (Arguedas et al., 2004).
- The 2-dose schedule separated by 6 months creates access challenges in mobile or underserved populations — single-dose programs have been evaluated in some countries with acceptable outcomes, but the US continues to recommend the 2-dose series.
🌫️ Scientific Uncertainties
Honest acknowledgment of what we don't yet know with confidence.
- Exact duration of immunity — models predict 25–40 years but real-world cohort data beyond 25 years is limited
- Whether single-dose schedules provide sufficient community protection (some countries use 1 dose)
- Optimal timing in immunocompromised children where antibody responses may be suboptimal
💉 Related Vaccines
Vaccines often given together or covering related diseases.
🌍 International Policy Comparison
How different countries approach this vaccine — revealing where global consensus is strong vs. where policy diverges.