October 15, 2008

Third Dose of Hep A Vaccine May Increase Immunity

An additional third booster shot of the hepatitis A virus (HAV) vaccine increased the chance of an HIV-positive person acquiring immunity to HAV and increased the number of antibodies against HAV after one year, according to the authors of a study published online in the Journal of Acquired Immune Deficiency Syndromes.

HIV treatment guidelines recommend that all people with HIV be vaccinated against HAV. Several studies, however, have found that people with HIV are less likely to develop antibodies to HAV following the traditional vaccination schedule, which is two doses given six months apart. Additional studies have also found that people with HIV who do develop HAV antibodies lose them more quickly than their HIV-negative counterparts.

To determine whether an additional “booster” shot of vaccine might improve responses, Odile Launay, MD, PhD, from the Université Paris Descartes in France, and her colleagues enrolled 99 HIV-positive patients between the ages of 19 and 55 who had never been vaccinated for HAV. Forty-nine of them got three doses of the vaccine at weeks 0, 4 and 24. The 50 other patients followed the standard vaccine schedule, with a shot at week 0 and the other at week 24.

Launay’s team found that about one year after the last vaccine dose in both groups, 86 percent of the patients in the three dose group and 70 percent of the patients in the two dose group had enough antibodies to HAV to provide protection. People in the three dose group also had many more antibodies remaining one year after the last dose than people in the two dose group. Though the difference in response rates appears large, it was not enough—given the small number of patients in the study—to reach statistical significance. This means that the difference in response could have occurred by chance. In general, people with lower CD4 counts and people who smoke were less likely in the study to develop HAV antibodies.

Though the additional vaccine dose did not reach statistical superiority to a standard vaccine schedule, the authors state that the evidence does tend to support an additional booster shot, particularly for vaccine non-responders, smokers and those with lower CD4 counts.

Search: hepatitis A virus, HAV, hep A, vaccine, vaccination, Odile Launay, Universite Paris Descartes

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