Hepatitis A is caused by a viral infection replicating in the liver. Like other forms of Hepatitis, acute infection results in fever, malaise, anorexia, nausea, abdonminal discomfort, dark urine and jaundice. Clinical illness does not typically last longer than two months, with 10-15% of patients having relapses lasting up to six months. Illness is less severe in children under the age of five, with infections typically being asymptomatic. The virus is transmitted person-to-person via the oral-fecal route.
At its introduction in 1995, the Hepatitis A vaccine was primarily targeted to individuals at increased risk of Hepatitis A infection such as international travelers. In 1999 the CDC recommended HepA vaccine for children > 2 years of age in a few states, counties or communities at higher risk of Hepatitis A. The recommendation for all USA children to receive this vaccine was not made until 2005.
Hepatitis A is a very low risk, especially for children under the age of 5 (see Disease Risk – HepA). The Hepatitis A vaccine contains aluminum adjuvant, a known neurotoxin (see Does Aluminum cause Vaccine-Injury?). Given the low risk of the disease and the potential vaccine-injury risk, a parent might consider whether the benefits of this vaccine are worth its risks.