Hepatitis A immunization for adults

General information
Hepatitis A (infectious hepatitis) is a viral liver infection. The hepatitis A virus is found in the stool of infected people and spreads primarily through fecal-oral contact. It spreads easily through contaminated food, water and sexual contact. Rarely, hepatitis A spreads through blood or blood products. Severity varies considerably from person to person. Some people have few or no symptoms, while others may be very ill for several weeks. Adults are usually more ill than children with hepatitis A, but most fully recover. Rarely, hepatitis A may lead to liver failure.
The hepatitis A vaccine ((HAV, Havrix, Vaqta) is made from an inactivated form of the hepatitis A virus.


Recommendations
The hepatitis A vaccine is specifically recommended for people who are at high risk for contracting the disease or of having complications from the illness, including homosexual and bisexual men and people who:
live in or travel to countries where hepatitis A is prevalent
use illegal drugs
have clotting factor disorders
have an occupational risk (work with hepatitis A infected primates or in hepatitis A research)
have chronic liver disease, including hepatitis C

Dose
The hepatitis A vaccine is given in two shots, with the second dose six to 12 months after the first (depending on the vaccine brand). If exposure to the infection is anticipated (such as during traveling), the first dose should be given at least four weeks before the exposure or travel.
For people over age 18, a combined hepatitis A and hepatitis B vaccine is available. You'll need three doses. The second dose is given one month after the first, and the third dose is given six months after the first. (This is the same schedule as the hepatitis B vaccine.)


Effectiveness/booster
Immunity begins within one month after the first dose. The vaccine is up to 100 percent effective in preventing the disease after two doses. Length of protection is uncertain, but may exceed 20 years. A booster is not recommended at this time.

Side effects
Side effects to the vaccine are minor. The most common include pain, soreness, redness and swelling at the injection site; fever; headache; and a general feeling of discomfort. These symptoms usually begin three to five days after the shot and last for one to two days. Very rarely, an allergic reaction may occur.

Who should wait to receive the vaccine
The vaccination may be postponed if you have a moderate to severe acute illness.

Who should not receive the vaccine
You should not receive the vaccine if you've had a serious reaction or severe allergy to a prior hepatitis A vaccination or any of its components.

Pregnancy-specific information
Vaccine safety during pregnancy has not been determined, but the theoretical risk is expected to be low. Discuss the benefits and risks of vaccination with your doctor if you're at high risk of exposure to the virus.