Q: "I've recently heard about some HIV studies being done relating to Pre-Exposure Prophylaxis, but would like to understand better how PrEP works. Also, what are the odds an HIV vaccine could be a reality soon?"
A: These are great and important questions! First of all let me touch a little on the Pre-Exposure Prophylaxis news. As you know, there was a recent large study called iPrEx done among MSM and transgender women. In the study, an anti-HIV medication called Truvada taken every day, along with condoms, treatment for other STDs and monthly HIV testing, helped cut the risk of getting HIV by about 44%. That’s really important and great news for the prevention field but there are still lots of questions that need to be answered.
For example, is it necessary to take the pill every day, or is it enough if it’s taken a few times a week, or right before & right after sex? What about long term side effects of taking Truvada? And how effective is this strategy in women and other populations, as communities of MSM are very diverse. In other words, there is a lot of excitement about these results; at the same time there is still a lot we need to learn about the effectiveness of taking anti-HIV medication for prevention of HIV.
Developing a safe and effective vaccine that prevents HIV infection or lessens the severity of infection in those who become infected is an important goal of the prevention field. But what are the odds that a vaccine could be a reality soon? It will likely be a number of years before we have a safe and highly effective HIV vaccine.
However, over the past year, there have been some exciting advances in the vaccine field which are helping to move the field forward. For example, researchers have been identifying pieces of the virus that are believed to be least likely to "change" and are common across many HIV viruses; or regions that are “weak spots” of the virus that, if blocked, could potentially prevent the virus from attaching itself to, entering and infecting the cell.
The goal is to use this information to make a vaccine and present to the immune system, teaching it to react to it quickly and effectively when and if the virus enters the body. In the human trials, there was exciting news almost two years about the results of a large vaccine trial done in Thailand. The group of participants who got the vaccine had a 31% lower HIV infection rate compared to those who got placebo. Although it still is not clear how the vaccine regimen accomplished it, work is being done to find out what exactly what responsible for this positive result. While the level of efficacy was modest, it demonstrates that an HIV vaccine is possible. This Thai study is also providing important information to build on.
Currently, the largest vaccine trial taking place in the United States is called HVTN 505; in fact, at present it is the only vaccine efficacy study going on in the world. It is being conducted in New York City and in 17 other cities around the U.S. HVTN 505 is hoping to add to this growing knowledge and get us closer towards a goal of finding a safe and effective HIV vaccine. If you want to find out more about this study go to TopsAndBottomsWanted.com or nycvaccine.org. -- Magda Sobieszczyk, MD, MPH