A new study conducted by researchers at the Yale School of Public Health and Oregon State University has evaluated the efficacy of the goals set by the Joint United Nations Programme on HIV/AIDS, also known as UNAIDS, and a hypothetical, partially effective HIV vaccine.

The study created country-specific mathematical models to predict the effects of the UNAIDS goals, the hypothetical HIV vaccine and the simultaneous implementation of both on rates of viral transmission and disease prevalence. The results suggest that meeting the UNAIDS goal would reduce rates of transmission and prolong survival, but in countries with a relatively high rate of transmission, even a partially effective HIV vaccine would have a much more significant impact. The findings, published in the journal Proceedings of the National Academy of Sciences of the United States of America on March 20, provide evidence for the importance of a vaccine in the effort to eliminate the virus.

“Achieving the UNAIDS target worldwide would be great, but for there to be a real turn with respect to the HIV pandemic, it might be important for there to be an introduction for at least a partially effective vaccine,” said Alyssa Parpia GRD ’22, a co-author of the study and Ph.D. student in the School of Public Health’s Department of Epidemiology of Microbial Diseases.

The UNAIDS global target, informally known as 90–90–90, was set in 2013 and aims to achieve its goals by 2020, according to the United Nations’ website.

It encourages nations to diagnose 90 percent of those affected with HIV, to provide 90 percent of those diagnosed with antiviral drugs and to achieve viral suppression 90 percent of the time among those given antiviral drugs.

If the goal is met, 81 percent of those with HIV will be on antiretroviral drugs and 73 percent will be virally suppressed. The current global average for HIV diagnosis is 53 percent. Of these, 75 percent have access to antiretroviral drugs, 77 percent of whom achieve viral suppression.

According to the study’s projections, if the UNAIDS goals were met, 22 million HIV infections could be averted while a partially effective vaccination alone would avert 17 million infections, though regional projections vary. The highest rate of averted infection was predicted to be in eastern and southern Africa, where just a vaccination would avert 7.7 million infections. In North America, the same intervention would prevent 216,000 infections. Even by meeting the UNAIDS standards and developing a partially effective HIV vaccine, the rising rates of HIV infection would not trend down, according to the study, as the interventions would only reduce the rate at which HIV incidence increases.

“Just implementing the UNAIDS goal won’t be sufficient to propel us into a future without HIV,” said Abhishek Pandey, a co-author and associate research scientist at the School of Public Health.

To arrive at that conclusion, models were first developed for 127 countries that together encompass 99 percent of the HIV/AIDS-affected population. Countries without current and available data were excluded. Data from historical trajectories of incidence and prevalence in each country were used to compile a country-specific HIV transmission model that stratified infection into the following groups: acute, chronic and undiagnosed, chronic and diagnosed, chronic and treated, chronic and virally suppressed, and those with AIDS.

Amber Tang ’18, a Yale Global Health Scholar and a coauthor on the study, said that the study’s model did not stratify by age or risk factor in order to be applicable to 127 countries.

“There is a good chance by 2025, a vaccine might be used somewhere,” Pandey said. “It is highly likely that there will be a vaccine.”