The decision not to continue the clinical trial of the country’s first AIDS vaccine based on the results of the Phase I trial is a setback for further research. The trial at the National AIDS Research Institute, Pune (NARI) using the adeno-associated virus (AAV) vector, started in February 2005, has found the vaccine safe and well-tolerated in all the 24 volunteers. However, the vaccine elicited only about 20 per cent immune response, falling short of the norms prescribed for putting it through the Phase II trial. That the immune responses were similar, despite the volunteers receiving a booster dose in Belgium and Germany, and a higher dose (compared to India), combined with a booster dose in Africa, is a clear indicator of AAV vaccine’s failure. A study undertaken prior to starting of the NARI trial found a reasonably high exposure to AAV, a non-pathogenic virus. People who are naturally infected by AAV would have antibodies against the virus. Though a clear finding is not available on how such antibodies would impact the immune response when vaccinated with AAV, it is perceived that they would not lower the immune response when higher doses of the vaccine are used, as in the case of the NARI trial.
That the setback has occurred despite the vaccine producing high immune responses in animals underlines the need to undertake human clinical trials. At the same time, more research has to be done to find the right vaccine candidates before undertaking human clinical trials. The time has come for serious efforts to be directed at research on microbicides and vaccines that would prevent infection in the first place. The brighter side of the NARI trial is that it has demonstrated that recruiting HIV uninfected people belonging to the low-risk category and retaining and doing the follow up on these individuals for a year are indeed possible. In fact, the Indian researchers should be given full credit for conducting the trial in an ethical manner without yielding to any external pressure. The real test now for the trial sponsors is to monitor the health of the volunteers for five years and provide medical care whenever required. Currently no drugs are available to cure HIV, and the failure of one possible vaccine candidate to progress to the Phase II trial underlines the imperative of redoubling efforts at evolving prevention strategies.