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Hepatitis A spreads primarily by fecal-oral contact; blood and secretions may also be infectious. Fecal shedding of the virus occurs during the incubation period and usually ceases a few days after symptoms begin; thus, infectivity often has already ceased when hepatitis A is diagnosed. Waterborne and foodborne epidemics occur, especially in underdeveloped countries. Eating contaminated raw shellfish is sometimes responsible. Sporadic cases are also common, usually as a result of person-to-person contact. Most infections are subclinical or unrecognized, and population surveys of anti-HA have revealed remarkably widespread exposure that varies with age, socioeconomic class, geography, and other factors. In some countries, > 75% of adults have been exposed.
Hepatitis usually resolves spontaneously after 4 to 8 wk. A favorable prognosis is less certain in Hepatitis B than in Hepatitis A infection, especially in the elderly and after transfusion, when mortality (for HepA)may reach 10 to 15%. Except for rare fulminant cases, hepatitis A invariably resolves, although early recrudescences occasionally occur; progressive chronic disease or cirrhosis does not develop.
I learned quite a bit about hepatitis A from reading the ACIP recommendation
for hepatitis A vaccine --
http://www.cdc.gov/epo/mmwr/preview/mmwrhtml/rr4812a1.htm
I already knew that 70% of kids who get hepatitis A are asymptomatic, but I didn't realize that concentrations of antibody by vaccination are 10 to 100 fold lower than those produced after natural infection. The diagnostic assays to measure lower levels of antibody had not been reviewed by the FDA as of 10 - 99 when this report was published. The absolute lower limit of antibody required to prevent HAV has not been defined.
The ACIP paper also said that: infants with passively acquired maternal antibody have reduced GMC's (geometric mean antibody concentrations) after vaccination.
This paper also states: Several studies are being conducted among infants and young children to evaluate whether simultaneous administration of hepatitis A with other vaccines affects the immunogenicity and reactogenicity of these vaccines.
This means that the recommendation came out before the studies were done!!!
Anyone in a state or county that is considering mandating hepatitis A should read this.
Cindy, Colorado