Though there have been extraordinary advances in HIV/AIDS treatment in the past several years, the disease remains a serious health concern worldwide. Promising developments in HIV vaccines are occurring all the time, but their potential long-term impact is still unknown. Using a novel mathematical model, a team at the Yale School of Public Health predicts that vaccines used in concert with other interventions have the potential to avert several million cases of the disease in the coming years.
In a paper published in the Proceedings of the National Academy of Sciences and edited by AIDS research pioneer and head of the National Institute of Allergy and Infectious Disease Dr. Anthony Fauci, the team examined data from 127 countries to determine how United Nations goals for diagnosing and treating HIV, as well as vaccination, would impact the number of future cases.
Led by Burnett and Stender Families Professor of Epidemiology (Microbial Diseases) Dr. Alison Galvani, the team’s mathematical model and research paper are the result of a collaboration at the School of Public Health’s Center for Infectious Disease Modeling and Analysis (CIDMA). Directed by Dr. Galvani, one of CIDMA’s goals is to use interdisciplinary mathematical modeling approaches to quantify the impact and cost-effectiveness of vaccines for a range of infectious diseases.
Quantifying the impact of these new interventions is essential policy making surrounding the disease and thus to overcoming the HIV epidemic. To do so, the team devised a mathematical model of progression, transmission and intervention of HIV infection. The model found that maintaining the status quo of treatment and diagnosis would lead to an estimated 49 million new cases of HIV/AIDS globally between 2015 and 2035. Factoring in an HIV vaccine, 17 million of those cases would be averted.
“Even if the ambitious UNAIDS goals regarding treatment as prevention are achieved, the additional benefit of a partially efficacious HIV vaccine would be enormous in terms of turning the tide on the pandemic and saving millions of lives across the globe,” said Dr. Galvani.
While vaccination is key to reducing the march of the disease, another part of the ongoing challenge in the battle against AIDS is the relatively low rate of testing and diagnosis. The Joint United Nations Program on HIV/AIDS (UNAIDS) has set a three-part, “90-90-90” global target for 2020: to diagnose 90 percent of HIV-infected people; to provide antiretroviral therapy (ART) to 90 percent of those infected; and to achieve viral suppression in 90 percent of those being treated with ART as well as 95 percent for each of the three components by 2030 in each country. Under status quo interventions, a median of 49 million new infections globally was projected over the next 20 years. It was predicted that the aspirational UNAIDS goals could avert 25 million of these new infections, and that an additional reduction of 6.3 million was projected with the introduction of a partially efficacy vaccine.
The knowledge gained by quantifying the impact of vaccination has the power to inform policy decisions on disease at national and international levels. The team’s paper also contains regional and country-level projections of the impact of HIV vaccine and interventions, which are important to predict specific strategies for region-specific concerns, and complications that arise from treatment.
“An exciting development in the field is the launching of an NIH-sponsored trial of a new HIV vaccine in South Africa. Given improvements on a former partial efficacy vaccine, I’m hopeful that this new vaccine will prove sufficiently efficacious to be licensed. Our results show that even a 50 percent efficacy vaccine would be highly impactful,” said Dr. Galvani.
Dr. Galvani co-authored the paper with Jan Medlock, a postdoctoral alumni of CIDMA and now a faculty member at Oregon State University, and CIDMA colleagues Dr. Abhishek Pandey, Dr. Alyssa Parpia, Dr. Amber Tang and Dr. Laura Skrip.