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Confab highlights latest HIV science


Dr. Anthony Fauci speaks at the IAS HIV conference in Mexico City. Photo: Liz Highleyman
Dr. Anthony Fauci speaks at the IAS HIV conference in Mexico City. Photo: Liz Highleyman  

The International AIDS Society Conference on HIV Science, taking place this week in Mexico City, highlights the latest HIV prevention, treatment, and cure research, including a potentially viable vaccine.

The meeting comes at a time when advances in treatment and prevention have dramatically lowered the likelihood of AIDS-related complications and death and reduced the risk of HIV transmission. But not everyone has access to these tools.

Dr. Anthony Fauci, the longtime director of the National Institute of Allergy and Infectious Diseases, estimated that effective antiretroviral therapy has prevented almost 10 million deaths and averted nearly 8 million new infections. And PrEP can lower the risk of acquiring HIV by around 99%.

"If you put those two things together — treatment as prevention and PrEP — if we put on ART all, or almost all [people with HIV], and give PrEP to all, or almost all, people at risk, we could rapidly end the epidemic," Fauci said. "But we don't live in a theoretical world. There's an implementation gap between these breathtaking scientific advances and what we're doing."

New numbers
These gaps were highlighted in a new report from UNAIDS released ahead of the conference. According to the latest estimates, 37.9 million people worldwide are living with HIV, 23.3 million have access to antiretrovirals, 1.7 million were newly infected, and 770,000 died from AIDS-related illnesses in 2018.

The report shows that some countries are meeting, or exceeding, the UNAIDS 90-90-90 targets — 90% of people living with HIV knowing their status, 90% of those diagnosed being on antiretroviral therapy and 90% of those on treatment having viral suppression by 2020 — but others are falling behind.

Worldwide, in 2018, 79% of people with HIV knew their status, 78% of those were on treatment, and 86% of those had undetectable viral load. But these averages mask wide disparities among countries. Nearly 90% of people in North America and Europe know their HIV status and are on treatment, but just 80% of those have undetectable viral load. Eastern Europe, Central Asia, the Middle East, and North Africa are falling behind on all three measures.

Looking at HIV prevention, the report says that only around 300,000 people worldwide are using PrEP — including 130,000 in the United States — but this is at best a rough estimate. Similarly, although people who inject drugs account for a high proportion of new infections in some regions, many lack access to syringe exchange and other harm reduction services.

Fauci cited San Francisco as one of the first cities to see a dramatic decrease in new infections by proactively going into the community to offer testing, getting people who test positive on treatment promptly, and putting at-risk HIV-negative people on PrEP.

Much of the news at the conference focused on prevention, including a report from an early study of a PrEP implant containing an experimental antiretroviral, islatravir, that could offer protection for a year.

Vaccine news
Researchers and advocates are also seeing a light at the end of the HIV vaccine tunnel. For two decades, studies showed little progress, but now a promising candidate is in large clinical trials.

The experimental vaccine, dubbed Ad26.Mos4.HIV, uses an engineered adenovirus vector — a harmless relative of the common cold virus — to deliver a mosaic of viral antigens designed to stimulate an immune response against the wide variety of HIV strains around the world.

A Phase 3 trial of the vaccine for men who have sex with men and transgender people is expected to start in September. The study, called Mosaico, aims to enroll 3,800 participants in North and South America and Europe. There will be 24 study sites in the United States, including the San Francisco Department of Public Health's Bridge HIV. A late-stage study of a similar vaccine is already underway for women in Africa.

The study aims to fill a need for people at risk for HIV who do not already have an effective prevention method, Bridge HIV director and Mosaico protocol chair Dr. Susan Buchbinder explained at the conference. Prospective participants will first be informed about, and helped to access PrEP. Only those who opt not to use PrEP will be eligible to join the study, but once they are enrolled they may decide to start PrEP and remain in the trial.

"They must have a real option to use PrEP and we acknowledge that participants' views on PrEP might change during the study," Buchbinder said.

While no one expects that this vaccine will be completely effective, Fauci said that on a public health level, even a 50% to 60% effective vaccine, in combination with other prevention methods, could have a dramatic impact on the global epidemic.

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