May 1996
ROCKVILLE, Md. — The Food and Drug Administration (FDA) approved Vaqta for active immunization against hepatitis A virus.
The vaccine, developed by Merck & Co., is an inactivated, whole-cell vaccine. It is the second hepatitis A vaccine to be available in the United States. The vaccine should be available this month.
It may be given to anyone 2 years of age and older. Children 2 to 17 years receive a single 0.5-mL dose with a 0.5-mL booster six to 18 months later; adults receive a single 1-mL dose with a booster six months later.
Vaqta is highly effective. In clinical trials, the vaccine provided near 100% protection against hepatitis A virus (HAV) one month after the booster dose, according to data presented to the FDA's Vaccines and Related Biological Products Advisory Committee.
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The vaccine is well-tolerated. The most common adverse event reported was local reactions at the injection site, which usually resolved within 24 hours of vaccination.
HAV often results in subclinical infection, especially among children. Adults older than 50 are at highest risk for severe symptoms, but a higher percentage of children are infected. Almost 30% of all reported cases are among children younger than 15 years old.
Clinical signs and symptoms include fever, malaise, anorexia, nausea, abdominal discomfort, dark urine and jaundice. Hepatitis A infection usually resolves within two months and does not result in chronic infection. Some people may experience prolonged or relapsing signs for up to six months.
The virus is spread through the fecal-oral route, most often through person-to-person transmission. It may also be spread through contaminated food or water.
An estimated 143,000 cases of HAV infection occur in the United States each year, with 1.4 million cases worldwide. The overall case fatality rate is estimated to be 0.3%.
The disease is cyclic, with outbreaks occurring every 10 to 15 years. The most recent outbreak in the United States was in 1989. Disease incidence varies by race and ethnicity, with Native Americans and Native Alaskans reporting the highest rates of disease.
- Werzberger A, Mensch B, Kuter B, et al. A controlled trial of a formalin-inactivated hepatitis A vaccine in health children. N Engl J Med 1992; 327: 453-57.
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