HIV vaccine trial nearly collapsed after U.S. aid freeze, last-minute funding patch kept it alive

A long-planned HIV vaccine trial in southern Africa came within days of collapse in early 2025 after U.S. aid officials issued stop-work orders tied to a sweeping freeze on foreign assistance. Scientists behind the project say they salvaged a pared-down version with new money from South African institutions and the Gates Foundation, allowing vaccinations to begin in late January 2026.

The trial grew out of the BRILLIANT Consortium, an Africa-led HIV vaccine development effort that won a $45 million grant from the U.S. Agency for International Development in 2023. Researchers convened in Zanzibar in early 2025 to finalize plans and prepare to enroll the first participants, according to an NPR report published Jan. 20, 2026.

Then the financing evaporated. President Donald Trump signed an executive order on Jan. 20, 2025, freezing foreign aid pending review, and researchers said USAID soon issued stop-work orders that halted spending and interrupted staffing, procurement and trial logistics. “That was crushing because we were about to enroll our first participants within the trial,” Penny Moore, a virologist at the University of the Witwatersrand in South Africa, told NPR.

The setback landed in a field that has absorbed repeated disappointments for decades. HIV mutates quickly, and its biology makes it difficult for the immune system to “see” key viral targets, complicating efforts to design a vaccine that protects against the many strains circulating worldwide. Reuters noted that scientists have pursued an HIV vaccine since the virus was first identified in 1983, without success.

BRILLIANT aimed to close that gap with an Africa-centered model: build vaccine-making capacity on the continent while focusing on the variants and immune responses most relevant to the region. South Africa remains a hub for HIV research in part because the country has the world’s largest population of people living with HIV, at more than 8 million. The work also reflects the continuing burden in sub-Saharan Africa. UNAIDS estimates 1.3 million new HIV infections occurred worldwide in 2024 and says women and girls accounted for 63% of new infections in sub-Saharan Africa that year.

Researchers behind BRILLIANT said the abrupt loss of U.S. funds threatened more than one trial. Equipment purchased with USAID funds, including laboratory refrigerators and centrifuges, remained in place, Moore told NPR, but the support structure to run large-scale clinical studies disappeared.

The consortium’s scientists did not abandon the effort. They scaled back the trial to South Africa only and began a scramble for alternative funding, Moore told NPR. They found a lifeline. The project secured support from the South African Medical Research Council and the Gates Foundation, NPR reported, though the replacement budget amounted to “about a twentieth” of the original USAID grant. That would put the restart funding near $2.25 million if measured against the $45 million award the consortium received from USAID. NPR noted that the Gates Foundation provides financial support to NPR.

With that financing, the trial returned to life after nearly a year of delay. NPR reported that screening began in communities near Cape Town and that the first injections were set to start “next week” after the Jan. 20, 2026, report, placing the first vaccinations in late January 2026.

The underlying vaccine concept targets one of HIV’s most promising scientific paths: inducing broadly neutralizing antibodies, rare immune proteins that can block many different strains of HIV. Moore told NPR that in some cases a single broadly neutralizing antibody can neutralize up to 90% of global viruses, but those antibodies usually develop too late to help someone already infected. To push that response earlier, BRILLIANT researchers have worked with genetic sequences from South African patients whose bodies generate those rare antibodies, Reuters reported. The project uses mRNA technology, similar to platforms used in some COVID-19 vaccines, to try to mimic and accelerate that immune response.

The approach aligns with a broader scientific shift toward “germline targeting,” a strategy designed to activate the specific early-stage B cells needed to mature into antibody-producing cells capable of generating broadly neutralizing antibodies. Reuters reported in May 2025 that early human trials published in “Science” showed encouraging results for germline-targeting vaccines, including mRNA-encoded nanoparticles produced by Moderna, though some participants experienced skin reactions.

Still, researchers say the BRILLIANT saga highlights how fragile vaccine development can be when funding changes quickly. In the United States, the National Institute of Allergy and Infectious Diseases informed scientists in May 2025 that it would not renew funding for major HIV vaccine consortia when current grants end in June 2026, “Science” reported, adding another layer of uncertainty for a field that often requires long timelines and stable financing.

Prevention tools continue to improve even without a vaccine. The FDA approved lenacapavir, a twice-yearly injectable for HIV prevention, on June 18, 2025, offering an alternative to daily oral PrEP for some patients. But scientists involved in BRILLIANT argue that even strong treatment and prevention options do not eliminate the need for a vaccine that can protect people before exposure, particularly in regions that carry the highest burden.

The revived South African trial will proceed on a smaller footprint than originally planned, but researchers and community liaisons say it preserves momentum and keeps a pipeline open for future candidates. “I’m afraid we will have to do it with or without because this matters too much to not finish the work,” Linda-Gail Bekker, director of the Desmond Tutu Health Foundation, told NPR.