May 18, 2017
Anthony S. Fauci, M.D., Director, National Institute of Allergy and Infectious Diseases
Carl W. Dieffenbach, Ph.D., Director, Division of AIDS, NIAID
Much progress has been made in HIV/AIDS research since the disease was first recognized in 1981. Today, lifesaving antiretroviral therapies allow those living with HIV to enjoy longer, healthier lives—an outcome that once seemed unattainable. Research supported by the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health (NIH), has proven that when antiretroviral therapy durably keeps HIV at undetectable levels, the risk that the treated individual will sexually transmit the virus to an HIV-negative partner is negligible. When implemented in communities, treatment as prevention is remarkably successful at preventing the spread of HIV infection. Pre-exposure prophylaxis, or PrEP, is another prevention strategy in which HIV-negative people take one pill a day to reduce their risk of acquiring the virus. This intervention is highly effective when individuals adhere to the drug regimen.
While these and other prevention tools have the power to dramatically decrease the incidence of HIV infection, a safe and effective vaccine would be transformative. More than two million new HIV infections occurred worldwide in 2015 alone, and this rate of infection has declined only slightly since 2010. A new NIH-funded modeling study suggests that a 50-percent effective preventative vaccine could reduce the number of people living with HIV by 36 percent globally over a period of 15 years. Together with the other medical and behavioral prevention modalities that have been proven to decrease the risk of acquiring HIV, a vaccine could change the epidemic’s trajectory, dramatically reducing the number of people who become infected with HIV.
Developing a safe and effective HIV vaccine is one of the most formidable challenges facing scientists today. HIV mutates rapidly, evading immune responses and thwarting the attempts of scientists to develop an effective vaccine. Only a minority of individuals living with HIV develop broadly neutralizing antibodies, a powerful type of antibody that can fight an array of HIV strains by binding to key sites on the virus. In those individuals who do develop such antibodies, they generally appear only after several years of infection, when the virus has already gained a strong foothold in the body.
Despite these challenges, scientists are working to develop a vaccine that may reduce the spread of HIV. On World AIDS Day 2016, NIAID and its partners launched HVTN 702, a phase 2b/3 HIV vaccine efficacy trial. This trial is the first HIV vaccine efficacy study to launch in 7 years, and is currently enrolling 5,400 men and women in South Africa between the ages of 18 and 35. This study will test an experimental vaccine regimen to see if it can extend and amplify the modest success of the vaccine candidate tested in RV144, a clinical trial in Thailand that showed a modest degree of efficacy in 2009.
Another component of the HIV vaccine research effort focuses on inducing the immune system to make the kind of broadly neutralizing antibodies that may protect people from HIV. The NIAID Vaccine Research Center and several NIAID grantees are at the vanguard of this effort.
Two multinational clinical trials testing an investigational anti-HIV broadly neutralizing antibody for preventing HIV infection began last year. Known as the AMP Studies, for antibody-mediated prevention, the trials will test whether giving people a broadly neutralizing HIV antibody as an intravenous infusion every 8 weeks is safe, tolerable and effective at preventing HIV infection among the study participants. With a projected enrollment of 4,200 men and women across three continents, the trials are designed to answer fundamental scientific questions for the fields of HIV prevention and vaccine research.
While the pursuit of a safe and effective HIV vaccine is challenging, this prevention strategy holds lifesaving potential and is NIAID’s highest priority for AIDS research. On this HIV Vaccine Awareness Day, we recognize and thank the thousands of HIV vaccine clinical trial volunteers, researchers, health professionals, activists and others who work together with us toward this goal.