Protective antibodies develop in response to infection and persist for life.

The protective role of anti-HAV antibodies has been demonstrated by the protection against hepatitis A resulting from passive immunization with serum immune globulin.

• travelers to developing countries,
  
• men who have sex with men,
  
• users of illicit drugs,
  
• persons needing frequent blood products, and
  
• people who have chronic liver disease.

 A second option for protecting people against hepatitis A is to administer antibodies that are already programmed to attack the virus. When people donate blood, the part of the blood carrying antibodies (the immune globulin fraction) can be separated. Because some blood donors are likely to have antibodies against the hepatitis A virus, pooled immune globulin from many donors is likely to contain antibodies against hepatitis A. This immune globulin can be injected into a person at risk for hepatitis A and will provide immediate but temporary protection against infection. Protection with immune globulin lasts two to four months depending on the dose. Immune globulin is used when immediate protection against hepatitis A is required. An example would be someone who is leaving immediately to travel to rural areas of a developing country. Such a traveler would also receive hepatitis A vaccine but would not have time to develop antibodies before departure.

These measures will reduce the risk that the exposed person will contract hepatitis A by 85% to 90% if given within two weeks of exposure.

Immune globulin currently is recommended for exposed persons over the age of 40 years.