Question

• In previously healthy infants, does the Hepatitis A vaccine protect against
  Hepatitis A infection when compared to placebo?
  

Clinical Bottom Lines

1. The virosome hepatitis A vaccine is effective in preventing hepatitis A infection and the shedding of virus in the stool of children 18 months to 6 years of age (NNT=7).

Summary of Key Evidence

1. This randomized, double blind trial investigated the efficacy of a single dose of virosome hepatitis A vaccine in 274 children, aged 18 months to 6 years, in Leon, Nicaragua. 239 of the 274 children were included in the primary efficacy analysis; 272 were included in the intent to treat analysis.¹
2. Anti-hepatitis A IgM was measured every 3 months during the 18 month long study, in order to investigate the presence of asymptomatic disease. Hepatitis A virus RNA PCR was performed on stool samples collected every 4 weeks throughout the study to search for asymptomatic viral shedding. Examinations by trained nurses looked for clinically overt hepatitis every 2 weeks throughout the study. Suspected clinically overt hepatitis was confirmed by ALT measurement and physician exam.
3. Efficacy of virosome hepatitis A vaccine was 100% after week 6 of the study. Number needed to treat to prevent one case of hepatitis A in this population was 7.
4. Although this study was sponsored by the drug company that manufactures the vaccine studied, it was valid in that the study was blinded, the groups were very similar, and the outcomes measured were important and appropriate.

Additional Comments

• Hepatitis A is a relatively rare, but occasionally fatal disease affecting 20,000-30,000 Americans each year.
• Children are a likely source of virus, as their infections are more commonly asymptomatic and they tend to have longer periods of shedding virus in their stool.
• The CDC has recommended Hepatitis A vaccination with an aluminum adjuvant Hepatitis A vaccine as a 2 shot series for all children in the US.²
• A virosome hepatitis A vaccine may be another option for widespread vaccination.
  

Citation

1. Perez OM, et al. Efficacy of Virosome Hepatitis A Vaccine in Young Children in Nicaragua: Randomized Placebo-Controlled Trial. Journal of Infectious Diseases. 2003; 188: 671-7.
2. Centers for Disease Control. Prevention of Hepatitis A Through Active or Passive Immunization: Recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Recommendations and Reports. 2006; 55(RR07): 1-23.

CAT Author: Meredith Riebschleger, MD

CAT Appraisers: Robert Schumacher, MD

Date appraised: October 11, 2006