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An HIV vaccine is within reach

But politics could derail the one thing to unlock it.

In January 2025, Linda-Gail Bekker stood inside a vaccine manufacturing plant and allowed herself to believe that the first HIV vaccine candidate conceived through African science and led by Africans might finally become a reality.

HIV has stubbornly resisted prevention via a vaccine. But in mRNA, scientists think they have finally found a technology to develop one.

mRNA, which was used for the successful Covid vaccines, is a way to agilely iterate and develop new candidate vaccines quickly.

Funding for HIV research has been yanked away by the Trump administration, and mRNA vaccines have faced political scrutiny, all threatening this breakthrough.

The vaccine would be built on mRNA technology, the same platform that had helped tame the Covid-19 pandemic. Bekker hoped it might finally crack the puzzle that had frustrated HIV researchers for more than four decades.

No virus has proved more evasive. Hundreds of HIV vaccines have entered testing; none has succeeded at providing durable protection against infection. And the need remains vast: In 2025, roughly 1.2 million new HIV infections were reported; anti-retroviral treatments have turned it into more of a survivable disease, but more than half a million people died from AIDS-related causes the same year. There is still no known cure.

So researchers like Bekker, an infectious disease specialist at the University of Cape Town, have more hope now, in part because there is finally a clearer idea of what an effective vaccine needs to do. It must coax the immune system into producing a particular type of protective antibody, a rare class of defender, capable of recognizing and disabling HIV despite the virus’s extraordinary diversity and rapid ability to mutate.

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No one yet knows how to reliably do that. But mRNA is uniquely suited to the task of finding out, vaccinologists say. Thanks to the platform’s speed and flexibility, researchers can iterate rapidly through the otherwise laborious process of designing, testing, and refining the series of vaccine components needed to guide the body toward making those essential antibodies.

At the start of last year, Bekker and her colleagues were ready to put that strategy to the test. The clinical trial for their new mRNA-based HIV vaccine was just on the verge of enrolling its first participants. But the project depended on the same backing that had sustained HIV vaccine research for decades: US government funding. Washington had long supplied roughly 90 percent of the world’s investment in the field. Then President Donald Trump returned to office.

Within hours of his inauguration, Trump signed an executive order freezing foreign aid. The $45 million contract from the US Agency for International Development (USAID) that was supposed to fund clinical trials like Bekker’s disappeared, as did a web of other funds, many routed through the National Institutes of Health (NIH), that had helped fuel the field’s progress for years.

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The timing could hardly be more cruel. After 40-odd years of chasing a shape-shifting foe, scientists believe they now know what kind of immune response an HIV vaccine must generate — and have in mRNA a powerful new tool for pursuing it. But just as many researchers have finally glimpsed a path to victory, the United States and much of the funding has pulled away from the fight.

From the outset, the target for preventing HIV was clear. Within a year of identifying the virus as the cause of AIDS in 1983, researchers had zeroed in on its envelope protein as the most promising point of attack for a vaccine.

Protruding from the virus’s surface in knobby clusters, the envelope protein acts like a molecular grappling hook, latching onto immune cells before pulling the virus itself inside. Without this feature, HIV cannot infect a cell.

Much as the coronavirus spike protein would later become the basis for Covid vaccines, this protein on the surface of HIV seemed an obvious bullseye. But identifying the target didn’t mean researchers could hit it. Most of what the immune system sees of the envelope protein is actually just a decoy. The parts that stick out and draw the strongest immune response are also its most changeable, differing from one strain to the next and mutating freely whenever antibodies close in, leaving the body to waste its firepower on a target that keeps slipping away.

Candidate vaccines kept making the same mistake. They would elicit plenty of antibodies, but not the kind that could keep up with the virus. Time and again, promising candidate vaccines generated excitement in the laboratory, only to come up empty when it mattered most in large-scale clinical testing.

The field’s fortunes started to change in the late 2000s when researchers........

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