There are two brands of hepatitis A vaccine currently available in the U.S. which may be used interchangeably. The second dose is also believed to be necessary for long-lasting protection. As neither of these vaccines has been available for as long as 5 years, how long the immunity lasts is unknown. Manufacturers recommend boosters after 7 years but experts feel that probably the immunity is good for over 20 years. Older adults may want to simply be tested first to see if they are already immune.
Chances are fairly good that they are and then they can avoid the whole debate.
There are both active and passive forms of immunization, with the same pros and cons. In addition, active immunization requires three shots over a six month period in order to be effective and even then doesn t work for everyone. Two further concerns are the other types of hepatitis and the people for whom the immunization is ineffective. For people on chemotherapy or other immunosuppressives or people with HIV or other immune deficiencies, the active immunization is less effective. They may have to have a higher does or simply use passive immunization.