Can the HAAVRIX (hepatitis A vaccine) cause hepatitis A infection?

HAVRIX Cannot Cause Hepatitis A Infection

HAVRIX is an inactivated (killed) hepatitis A vaccine that cannot cause hepatitis A infection because the virus has been completely inactivated through formalin treatment during manufacturing. 1

Why HAVRIX Cannot Cause Hepatitis A

Vaccine Preparation Process

• HAVRIX contains formalin-inactivated hepatitis A virus that has been propagated in human fibroblasts, purified, and then completely inactivated, making it impossible for the virus to replicate or cause infection 1
• The inactivation process is similar to that used for inactivated poliovirus vaccine, which has a long-established safety record 1
• All hepatitis A vaccines licensed in the United States are inactivated vaccines—none contain live virus 2

Clinical Evidence of Safety

• In clinical trials involving approximately 40,000 children, no serious adverse events were reported that were attributable to HAVRIX 1
• Double-blind, placebo-controlled trials demonstrated that HAVRIX is highly effective (94% efficacy) without causing hepatitis A disease 1, 3
• Post-marketing surveillance of approximately 188 million doses worldwide (including 50 million in the United States) has not identified hepatitis A infection as a vaccine-related adverse event 1

Common Adverse Reactions (Not Hepatitis)

Expected Vaccine Reactions

• The most common adverse events are mild and include fever, injection-site reactions, rash, and headache—none of which represent hepatitis A infection 1
• Local and systemic reactions occur in less than 5% of vaccinees and are generally mild 4
• These reactions represent normal immune system responses to the vaccine, not infection 5, 4

Important Clinical Distinction

IgM Anti-HAV After Vaccination

• HAVRIX can induce detectable IgM anti-HAV in 8-20% of adults within 2-3 weeks after vaccination, which may be confused with acute infection if tested during this window 1
• This IgM response is an immune reaction to the vaccine antigen, not evidence of active hepatitis A infection 1
• Clinical pitfall: Do not misinterpret post-vaccination IgM anti-HAV as evidence that the vaccine caused infection—this is simply an antibody response to inactivated viral antigens 1

Contraindications (Unrelated to Infection Risk)

• HAVRIX should not be given to persons with severe allergic reactions to previous doses or vaccine components 1
• The vaccine's inability to cause infection means it can be safely administered to immunocompromised persons 1
• Pregnancy is not a contraindication because the inactivated vaccine poses no infection risk to the fetus 1