It took an extra “booster-dose” of the hepatitis A virus (HAV) vaccine for HIV-positive men who have sex with men (MSM) to have an equivalent response to the vaccine as HIV-negative men. This finding was reported September 12 at the 50th Annual Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC) in Boston.
HIV-positive MSM are about three times as likely to become infected with HAV than HIV-negative MSM. For this reason, the Centers for Disease Control and Prevention (CDC) in Atlanta recommends that all HIV-positive MSM receive the HAV vaccine. Numerous studies have found, however, that vaccines generally don’t work as well in people with HIV, particularly those with low CD4 counts.
To determine whether an extra booster dose of the vaccine might help improve the immune response of HIV-positive MSM to the HAV vaccine, Yu-Tzu Tseng, MD, from the Taipei City Hospital in Taiwan and his colleagues offered the HAV vaccine to 476 MSM. All of the 187 HIV-negative men received two doses of the vaccine—the first at the beginning of the study and the second six months later—as did 135 of the HIV-positive men. This is the standard dosing schedule for the HAV vaccine. An additional 154 HIV-positive men received the standard doses plus an extra dose one month after the first, for a total of three doses.
Tseng and his colleagues performed HAV antibody tests at the beginning of the study, again right before administering the six-month dose, and then six months after that. The researchers reported data on the results of the antibody tests conducted right before administering the six-month dose. At that time point, the HIV-negative men and the HIV-positive men receiving the standard vaccination schedule would have received only the first of their two doses. The HIV-positive men receiving the booster dose of the vaccine would have received the first two out of three.
Tseng’s team found that HIV-positive men needed the extra dose to bring their response rates up to the level of the HIV-negative men. When the HIV-negative and HIV-positive men who received only one dose of the vaccine were compared, 63 percent of the HIV-negative men had a HAV antibody response compared with only 39 percent of the HIV-positive men. In the HIV-positive men who received the extra dose, however, response rates were 64.9 percent.
An additional analysis that looked at the influence of CD4 cell counts revealed that HIV-positive men with CD4 counts under 200 had a very poor antibody response to the vaccine. In HIV-positive men with CD4s under 200, none of those who received two doses of the vaccine responded. The authors did not report response rates for those with less than 200 who received the extra dose of the vaccine.