Killed hepatitis A vaccines are prepared from virus grown in tissue culture and inactivated with formalin. The first such vaccine was licensed in 1992 and several preparations are available, including a combined hepatitis A and B vaccine. These vaccines are highly immunogenic and provide long-term protection against infection.
In areas of high prevalence, most children have antibodies to HAV by the age of 3 years and such infections are generally asymptomatic. Infections acquired later in life are of increasing clinical severity. It is important, therefore, to protect those at risk because of personal contact or because of travel to highly endemic areas. Other groups at risk of hepatitis A infection include staff and residents of institutions for the mentally handicapped, daycare centres for children, sexually active male homosexuals, intravenous narcotic drug abusers, food handlers, sewage workers, health care workers, military personnel and members of certain low socioeconomic groups in defined community settings. Patients with blood coagulation defects and patients with chronic liver disease should be immunised against hepatitis A.
In some developing countries, the incidence of clinical hepatitis A is increasing as improvements in socioeconomic conditions result in infection later in life; protection by immunisation would be prudent but strategies are yet to be agreed. Global control of hepatitis A will
require universal immunisation of infants and will become possible when HAV vaccine is combined in a polyvalent form with other childhood vaccines such as diphtheria, pertussis, tetanus, measles, rubella, mumps and hepatitis B.
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