Washington, DC - Since the first cases of what would become known as HIV/AIDS were initially reported in 1981, scientists and public health officials have been working to better understand HIV, develop strategies to effectively treat and prevent infection, and bring about an end to the pandemic. This effort remains a critical focus globally and for the United States.
We have the tools at hand that could—if fully implemented—end the HIV pandemic. Large clinical studies have proven that individuals with HIV who use antiretroviral therapy to achieve and maintain an undetectable viral load do not sexually transmit HIV to others—a concept known as undetectable = untransmittable (U=U). People who are at high risk for HIV can take a single daily pill known as PrEP, or pre-exposure prophylaxis, that is highly effective at protecting them from the virus. In addition, post-exposure prophylaxis, or PEP, provides a highly effective emergency means of preventing HIV transmission from a recent high-risk exposure and can serve as a bridge to PrEP.
In his State of the Union Address earlier this year, President Donald J. Trump announced his Administration’s goal to end the HIV epidemic in the United States within 10 years. Ending the HIV Epidemic: A Plan for America (link is external) aims to reduce new HIV infections in the United States by 90 percent by 2030. This approach is feasible in large part because the majority of new HIV cases in the United States are concentrated in certain geographic areas and within certain populations. More than 50 percent of new HIV diagnoses occur in 48 counties; Washington, DC; and San Juan, Puerto Rico. Additionally, seven states have a disproportionate occurrence of HIV in rural areas. In addition, young African American and Latino men who have sex with men bear a disproportionate burden of new infections. Targeted implementation of scientifically proven tools for HIV prevention, diagnosis, and treatment, as well as resources, expertise and technology, in these locales and among these populations could end the domestic HIV epidemic.
While the ambitious Plan for America aims to end HIV as an epidemic within the United States in 10 years, achieving a durable end to the pandemic will almost certainly require a safe and effective HIV vaccine. The development and deployment of an effective vaccine would provide long-lasting protection and alleviate the need to depend heavily on prevention methods that require continued access and adherence. Such a vaccine, along with the optimal implementation of existing HIV treatment and prevention strategies, would achieve the goal of durably ending the HIV epidemic in this country and worldwide. For geographic areas where the implementation of treatment and prevention is complicated by various social, economic and political concerns, a vaccine is critical to halting the epidemic. Indeed, even in countries with a good track record of implementing HIV treatment and prevention tools, a vaccine would hasten the end of the epidemic and ensure its durability.
In this regard, NIH is pursuing two scientific paths to develop a safe and effective HIV vaccine. One path aims to build on the promise of modest results seen in RV144, the U.S. Army-led HIV vaccine trial in Thailand. RV144 was the first and only trial to-date to demonstrate that an HIV vaccine can protect against infection. The Phase 2b/3 HIV vaccine trial HVTN 702 began on World AIDS Day 2016 and has nearly completed enrollment of 5,400 men and women in South Africa. Another large vaccine efficacy clinical trial called HVTN 705/HPX2008 or Imbokodo launched in 2017. This Phase 2b proof-of-concept trial is evaluating an investigational vaccine regimen designed to induce immune responses against a variety of global HIV strains. This trial is nearing complete enrollment of 2,600 women in sub-Saharan Africa.
The second path to developing an HIV vaccine is based on theory and involves studying the body’s immune response to HIV infection and generating and enhancing those responses through vaccination. The main theoretical approach to developing an HIV vaccine aims to prevent HIV by eliciting broadly neutralizing antibodies (bNAbs) (link is external)—antibodies shown in the laboratory to stop most HIV strains from infecting human cells. Some people living with HIV naturally produce bNAbs. However, these antibodies develop too late after initial infection to clear the virus. Scientists at NIH and other institutions have isolated numerous bNAbs from people living with HIV and are working to develop vaccines that elicit these antibodies in healthy people.
Two experimental structure-based vaccines aimed at eliciting bNAbs directed against various components of the HIV envelope are in or near the early stages of human study. A Phase 1 trial testing the BG505 SOSIP.664 gp140 trimer vaccine candidate is currently enrolling men and women in Boston; Seattle; and Nairobi, Kenya. Planning for a Phase 1 clinical trial to test a fusion peptide HIV vaccine developed by scientists at the NIAID Vaccine Research Center also is under way.
Additional concepts that use various viral vectors that have HIV-gene inserts that express immunogens of interest are in early development and are approaching clinical trials. These vectors include adenoviruses, modified vaccinia Ankara (MVA) and cytomegalovirus.
In addition to attempts to elicit antibodies to HIV via a vaccine, two multinational clinical trials are testing whether it is possible to prevent HIV by directly infusing people with bNAbs several times a year. Known as the AMP Studies, for antibody-mediated prevention, these trials have completed enrollment of 4,600 men and women across four continents. If these studies prove successful, it will provide a rationale for using bNAbs as tools to prevent HIV infection. In addition, it would provide the proof of concept that if vaccines induce these bNAbs, such vaccines would be successful in preventing HIV infection.
The pursuit of a safe and effective HIV vaccine holds lifesaving potential for people worldwide and is among the highest HIV research priorities for NIH. 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 with us toward this goal.