Dozens of students freshly trained as recruiters streamed into the dormitories on the sprawling green campus of the University of Zambia on a muggy morning in March. They wended their way past piles of papers, laundry and instant noodle packages, pouncing on any classmate who slowed long enough to listen to their pitch:

“Come with me, right now, and get an injection! It will protect you from H.I.V. infection for the next six months. It will take two minutes! And it’s free!”

It was an early experiment in delivering the most scientifically advanced weapon that exists in the fight against H.I.V. targeted to the people who need it most: young African women who, statistically speaking, are at greater risk of infection with the virus than anyone else on earth.

A line soon formed, and students filed one after another into a small room, pulled up their T-shirts and received two injections, on either side of their navels, of a drug that prevents infection in people exposed to H.I.V.

For the researchers, clinicians and health officials who gathered on the sidelines to watch, it was a hopeful moment, at a time when Zambia’s H.I.V. response has been badly damaged by the Trump administration’s overhaul of foreign aid.

In clinical trial results published in 2024, the drug, called lenacapavir, showed an astonishing 100 percent protection from infection in patients who received injections every six months. Ever since, there has been a concerted push to get the medication to sub-Saharan Africa.

When the Trump administration made deep cuts to foreign aid last year, there were fears that it would renege on a Biden administration commitment to help get lenacapavir to developing countries. But the State Department has not only honored that commitment, it has also recently increased the investment. The department said it would work with an international health organization to help fund the purchase of enough of the drug to reach three million people by the end of 2028.

“This is a really exciting opportunity to actually bend the curve of the epidemic,” Jeremy Lewin, the top official for foreign aid at the State Department said in announcing the expanded commitment last month. He added, “Lenacapavir is one of the best ways to actually have a chance at ending it.”

Still, whether the distribution of the drug can achieve its full promise of eventually ending the H.I.V. epidemic here is far from clear. The Trump administration’s other aid cuts have left the country’s health system so fragile that it may not have the infrastructure — to do tests, to deliver the drug, to keep records — necessary to get the drug to all those who need it. And it’s not clear whether Zambia will receive enough donated doses — or be able to buy enough — to have a meaningful impact on rates of H.I.V. transmission.

Gilead Sciences, which developed lenacapavir, sells the drug for more than $25,000 per patient per year in the United States. But Gilead has also licensed several generic drug companies to produce it, and they are expected to start supplying it for about $40 per person per year in 2027. In the meantime, Gilead is making the drug at a no-profit price (estimated to be about $100 per person per year). The Global Fund to Fight AIDS, Tuberculosis and Malaria and the United States’ H.I.V. program are supplying it in eight developing countries so far with plans to reach 24 countries by the end of this year.

Zambia was one of the first two countries in Africa to receive lenacapavir, and in December it started offering it to women in a maternal health clinic at the national teaching hospital in Lusaka.

On a March morning, harried nurses at the clinic were weighing patients, checking blood pressure, listening for fetal heartbeats, examining newborns and testing for H.I.V. And they were explaining lenacapavir.

Many women are eager to try it, said Dr. Suilanji Sivile, the technical director of the national H.I.V. program. But the clinic give it to just a few each week because they are not sure how much of the drug Zambia will receive, and when it will arrive. The upheaval in the aid relationship with the United States has clouded planning and the delivery timeline.

“You cannot start someone without knowing you will be able to give them their next dose when they return in six months’ time,” Dr. Sivile said.

Mavis Mwanza, 19, was one of the women who made the cut in March. Four months into her first pregnancy, she had heard about lenacapavir on social media and thought it seemed like a good idea. She lives far from the hospital, she said, so H.I.V. prevention she could get once, at this appointment, and then not think about again for months, would be a relief.

Ms. Mwanza got her first dose of lenacapavir (actually two injections plus two tablets that a patient takes the first time they receive the drug) from a midwife, in a clinic room so small the door could not open all the way.

Glenda Malyangu, the nurse who oversees the H.I.V. program in the clinic, peered over the top of her glasses at benches packed with women, many holding new babies bundled in blankets.

She wants to put every woman who tests negative for H.I.V. on pre-exposure prophylaxis, or PrEP, a medication to prevent them, and their babies, from getting infected. And she has been frustrated by the lack of options. For a decade there has been a daily pill she can offer, but that method is impractical and unpopular with young women, the group she most urgently needs to protect.

“But this lenacapavir, it is popular,” she said. It works for the women she sees because it is discreet — no need even to mention it to a partner — and does not require a pill every day. They can stop thinking about H.I.V. risk for a full six months.

But explaining how it works and giving the shot is more work for her team than handing over a bottle of pills. “It would have been easier if we were many,” she said. The clinic staff was cut by two-thirds last year, when many positions funded by the United States were eliminated.

This has meant that lenacapavir is being introduced into Zambia’s health system when it is already under new strain. More than 1.4 million Zambians live with H.I.V. The country was receiving close to $400 million a year through the U.S. President’s Emergency Plan for AIDS Relief, or PEPFAR, program, to provide treatment, testing and prevention, before President Trump took office. The H.I.V. program has been significantly scaled back, while the government negotiates a contentious new health funding agreement that the State Department has tied to giving American companies more access to Zambian mineral resources.

Under that agreement, Zambia, one of the world’s poorest countries, would receive about half the money it used to, tapering to zero over five years.

While a major challenge in delivering lenacapavir is lack of personnel, Ms. Malyangu said, there is another that is more basic: water. The country’s major maternal health center lacks reliable clean water to give patients so they can swallow the pills that accompany for their initial injection.

To adjust to the reduced budget, Zambia has scaled back its H.I.V. testing and prevention programs. Dr. Lloyd Mulenga, the head of the program, said he hoped that rolling out lenacapavir could cut new infections enough to make up for much of what has been lost.

But that will require health workers to do education and build demand for the new injection; testing to see who is H.I.V. negative and eligible to receive it; and a records system to track when people need to return for their next dose and make sure they show up to get it. To slow the epidemic, lenacapavir will have to reach every corner of the country.

“We will need new partnerships, new funding, new resources,” Dr. Mulenga said.

And lenacapavir will have to be delivered outside of medical facilities — PrEP, he noted, is for healthy people, and healthy people do not go to hospitals.

That is what sent the recruiters into the university dormitories for a first experiment in March, shepherding interested students into the campus clinic, while a team from the Ministry of Health carted in boxes of lenacapavir. Esther Banda, a second-year arts student, joined the line.

College is expensive, she said, and she and her friends cannot get by on what their families can afford to give them. So, she said: “You find someone like a boyfriend and he pays you something, it might be one time or you see him a few times.” One of those meet-ups might leave a young woman with $25 in her pocket at the end of the night — money that, Ms. Banda said, pays for food and cellphone airtime and manicures.

The students — many young men turned up, too — cycled in and out of the injection room, a five-minute appointment that protected them for the next six months.

But the university event had the support of five internationally funded agencies whose continuing presence in Zambia is in question. Even with all the extra support, the rollout began hours late: Someone on the campus clinic staff had been supposed to leave an on-paper authorization for the health ministry, but did not turn up, so a half-dozen health care workers sat around for hours, and students brought in by the recruiters drifted away.

The names and phone numbers of students who eventually got the injection were recorded in a variety of paper files, stacked in the leftover boxes; there was no electronic record, making it harder to track the students down for their next injections.

Ms. Banda’s hurried appointment concluded without her receiving any information about what she should do to get a crucial follow-up dose six months later. A half-dozen other appointments a New York Times reporter observed ended the same way.

“I think this could be very good for me,” said Ms. Banda, 22, who came from the dorm to get lenacapavir still in her pink pajamas. “I hope that I can find it again in six months. I hope it’s still free.”