Update on plans for future research studies to build on the modest success of RV144
The Thai Phase III HIV vaccine clinical trial, also known as RV144, was the largest HIV vaccine study ever conducted and involved more than 16,000 volunteers in Thailand. This U.S. Army-sponsored HIV vaccine study showed that an investigational HIV vaccine regimen was safe and modestly effective (31.2% efficacy, mITT analysis) at reducing the rate of HIV infection compared to placebo.
MHRP and the RV144 collaborators, which include the NIAID, have been working extensively with international experts to exploit these results quickly and effectively. Within the next few months, laboratories around the world will begin examining the blood of trial participants to look for clues as to why the vaccine had some success in preventing HIV infection. These pilot and case-controlled studies are aimed at exploring potential correlates of protection, and results should be available in about one year.
The collaborators are also planning clinical studies to extend and build on the modest success of RV 144. Results suggest that the vaccine regimen protected people at lower risk of infection, and the protection appeared to wane over time. One proposed study involves boosting some of the volunteers from RV144 to see if this will extend and increase the immune response (a “boost” is an additional vaccine dose given after the primary doses to increase the immune response to the original vaccine antigens).
Another proposed study will recruit several hundred new volunteers in Thailand who will receive a similar vaccine regimen as in RV144, plus an additional boost at 12 months. This study would provide insight into the benefit of the additional boost and collect more blood and some tissue samples so that extensive research can be conducted on the study participants’ immune responses.
Future clinical studies will likely involve populations with different risk factors/HIV incidence, and will also be executed in other parts of the world where other strains of HIV circulate. While these studies will take much longer to plan and execute, they will provide important clinical data on how to develop a more effective vaccine that could be used globally.