Big news this morning: A new vaccine tested in Thailand reduces the risk of HIV infection by 31%, giving scientists hope that a vaccine against the epidemic is indeed possible.
Scientists have been trying to develop an HIV vaccine for decades, with no success. One trial even had to be stopped because vaccinated patients appeared to be at higher risk of getting the virus. But in a study of Thai men and women at average risk of contracting HIV, 51 of the 8,197 who were vaccinated became infected, compared with 74 of the 8,198 who received a placebo shot. The AP calls this 31% reduction in risk "modest," but it may pave the way for a better vaccine later on. Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, which cosponsored the study, says, "It gives me cautious optimism about the possibility of improving this result. [...] This is something that we can do."
The vaccine is actually a combination of two previously tested vaccines. One, AIDSVAX, was meant to stimulate the production of antibodies to fight off HIV infection. The other, ALVAC, was meant to help fight HIV more effectively after infection through a process called "cell-mediated immunity." Neither vaccine had worked on its own in clinical trials. And the combination did not reduce the amount of the virus in the bloodstream of those who did get infected. Since the combined vaccine appeared not to affect any of the usual indicators of immunity to the virus, Fauci said its success "tells us how much we have to learn" about what really keeps people from getting infected.
It's not clear whether a 31% reduction in risk is enough for the vaccine to be distributed widely in Thailand or elsewhere. The researchers said they would offer the vaccine to the control group if it showed a "clear benefit," of greater than 50% reduction. And Fauci said that scientists usually would not try to license any vaccine less than 70-80% effective. It's more likely that the results of the study will be used to try to develop other, better vaccines. Says Fauci, "If you have a product that's even a little bit protective, you want to look at the blood samples and figure out what particular response was effective and direct research from there."
Skeptics caution that it's too early to tell whether this vaccine will ever lead to a more effective one. AIDS researcher John P. Moore says, "The rush to judgment is something we should try to avoid. We shouldn't be drawing radical conclusions based on a few raw numbers." Still, it's tempting to see this vaccine as a glimmer of hope in the battle to end one of the biggest public health nightmares of the past 25 years. HIV/AIDS has become such a huge part of modern medicine and sexual politics that it's now hard to imagine a world where it doesn't exist, but anyone born before the early 80s has lived in such a world. Cultural critics sometimes refer to the pre-HIV era as a more "innocent" time, when sex didn't have the same risks it now does. And while plenty of other STDs exist, and pregnancy will always be a concern, it's interesting to imagine what would happen if we could all be vaccinated against one of sex's most dire consequences. Would sex education change? Would abstinence-only types have more trouble arguing that premarital sex was inherently bad for you? Would our puritanical-yet-sex-obsessed culture become a little more at ease with sexuality? Let's hope we get the chance to find out.
Combo Vaccine Reduces Risk Of HIV Infection, Researchers Say [CNN]
For First Time, AIDS Virus Vaccine Effective In Trial [AP, via LA Times]
AIDS Vaccine Experiment Yields Unanticipated Results [Washington Post]
For First Time, AIDS Vaccine Shows Some Success In Trials [NYT]