Co-authored by Margaret (Peggy) Johnston, Ph.D., Senior Scientific Consultant, NIAID.
HIV Vaccine Awareness Day provides an opportunity to acknowledge the more than 35,000 individuals who have volunteered for preventive HIV vaccine trials over the past 25 years. Without their participation, the modest success that we have achieved thus far would not have been possible. Many thousands more volunteers will be needed if we are going to achieve our ultimate goal of developing a safe and effective vaccine that will help stop the spread of HIV worldwide.
Since the discovery of HIV in 1983, dozens of antiretroviral agents have been licensed and have resulted in dramatic improvements in the quality of life and life expectancy of millions of HIV-infected individuals. In addition, global access to these life-saving therapies has been progressively increasing, which not only benefits the HIV-infected individual, but makes them less likely to transmit the virus to their sexual partners. However, for every individual who gains access to these therapies globally, two to three individuals become newly infected. Treatment alone is not likely to rid the world of AIDS; the need for improved approaches to prevent new HIV infections is compelling.
Fortunately, through the combined support of the National Institute of Allergy and Infectious Diseases (NIAID) at the National Institutes of Health (NIH), other US Government agencies, nonprofit organizations, and others, progress in developing new technologies that prevent HIV infection has been notable. Adult male circumcision resulted in greater than 50% protection against HIV acquisition among heterosexual men in several African countries. A once a day pill was shown to reduce new infections in men who have sex with men by 44%, and protection appeared even higher in those men who adhered to the daily drug regimen. Promising results have also been achieved with a vaginally applied microbicide, which protected 39% of women in a trial in South Africa. Again, protection was higher in those who adhered to the drug use schedule. Another exciting finding is that a vaccine provided 31% protection in a heterosexual population in Thailand. Interestingly, efficacy appeared to be 60% in the earlier stages of the trial before the vaccine induced immune responses waned.
Our goal now is to improve upon these latter results. Why did this vaccine work and can we build on that knowledge to design more effective vaccines? Will a vaccine adjuvant or vaccine vector increase the level of protection? Can efficacy be achieved in higher incidence populations and in populations exposed to different subtypes of HIV? Will keeping vaccine induced immunity high for a longer period of time increase the duration of protection? Are there alternative approaches to ensuring that effective immunity is present when individuals are exposed to HIV? These are all questions that NIAID together with our partners plans to address through continued basic and clinical research.
Conducting additional clinical vaccine research presents technical, resource and logistical challenges that will require multi-sector, international partnerships to address. Engagement of the private sector and regulatory agencies will help map a path to vaccine licensure. Clinical trial specialists will apply their best strategic thinking to determine how multiple trials can be efficiently and effectively accomplished. Participation of government officials and researchers in the countries where trials will be conducted will ensure that trials are approved and carried out expeditiously and according to the highest ethical standards. Strong partnership with affected communities and trial volunteers will help make certain that they understand the risks and benefits of participation in HIV vaccine trials. Only through continued support and participation of communities and individual trial volunteers will we achieve the goal of identifying a safe and effective preventive vaccine, which would be an invaluable addition to the tool box of prevention approaches.