94 percent showed up on schedule; not a single person tested positive
In six Brazilian cities, a year-long study quietly answered one of public health's most persistent questions: not whether a medicine works, but whether people can sustain it. Among 1,400 young people from communities bearing the heaviest burden of HIV, a bimonthly injection proved far easier to keep than a daily pill — and that difference, measured in adherence rates and absent infections, may reshape how Brazil approaches prevention for a generation.
- Brazil recorded nearly 46,500 new HIV infections in 2023, with young sexual and gender minorities absorbing a disproportionate share — the prevention gap is not hypothetical, it is counted in lives.
- Daily oral PrEP, the existing public health standard, protected users only 48% of monitored days in the broader comparison group, meaning most people were unprotected most of the time.
- When given a genuine choice, 83% of study participants chose the injectable option — a signal that demand already exists and that the barrier has been logistical, not motivational.
- Injectable cabotegravir achieved 94% adherence and zero HIV infections across the study period, against one infection and 58% adherence in the oral group — a gap too wide to attribute to chance.
- Anvisa approved injectable cabotegravir in 2023, but the Ministry of Health has yet to commit to a timeline for incorporating it into the SUS, leaving the most promising tool approved but not yet deployed.
Between October 2023 and September 2024, researchers from Brazil's Oswaldo Cruz Foundation followed roughly 1,400 young people across Rio de Janeiro, São Paulo, Salvador, Campinas, Florianópolis, and Manaus as they navigated a choice: take a daily pill to prevent HIV, or receive an injection every two months. The study, ImPrEP CAB, presented its findings at a major international conference on retroviruses, and the results were difficult to ignore.
Participants were between 18 and 30 years old — men who have sex with men, transgender people, and non-binary individuals, none of whom had used PrEP before. When offered both options, 83 percent chose the injectable form, which delivers the drug cabotegravir once every eight weeks. The 17 percent who chose the daily oral pill — a tenofovir and emtricitabine combination available through Brazil's public health system since 2017 — faced a harder road.
The adherence gap was stark. Injectable users kept 94 percent of their scheduled appointments and recorded zero HIV infections over the study period. Oral users were protected only 58 percent of monitored days, and one person in that group contracted HIV. When researchers compared these figures to roughly 2,400 existing oral PrEP users across 14 cities, the picture darkened further: that group achieved just 48 percent coverage, and nine people became infected.
The broader context gives these numbers weight. Brazil logged 46,495 new HIV infections in 2023 — about 2,000 more than the previous year — with men aged 20 to 29 accounting for more than 40 percent of cases. The country has made genuine strides in treatment, cutting AIDS-related deaths by nearly a third over the past decade, but prevention among young minorities remains stubbornly difficult.
Injectable cabotegravir received regulatory approval from Anvisa in 2023. Whether it enters the public health system is still under Ministry of Health review, with no timeline announced. The ministry noted Brazil has doubled its PrEP users in three years to 119,000, and reaffirmed the goal of ending HIV as a public health crisis by 2030. What the study makes plain is that the path to that goal may depend less on the medicine itself than on whether the health system makes it possible to actually take it.
Between October 2023 and September 2024, researchers at Brazil's Oswaldo Cruz Foundation tracked roughly 1,400 young people across six cities—Rio de Janeiro, São Paulo, Salvador, Campinas, Florianópolis, and Manaus—as they chose how to take PrEP, the medication that prevents HIV infection. The study, called ImPrEP CAB, presented its findings recently at a major international conference on retroviruses and opportunistic infections in the United States, and the results were striking: those who opted for an injection every two months stuck with it far more reliably than those who took a daily pill.
The participants were ages 18 to 30, drawn from groups hit hardest by HIV in Brazil—men who have sex with men, transgender people, and non-binary individuals. None had used PrEP before. They came to public health clinics either seeking the medication or to get tested for HIV. When given the choice, 83 percent chose the injectable form, which delivers the drug cabotegravir once every eight weeks. The remaining 17 percent selected the oral version, a daily combination pill of tenofovir and emtricitabine that Brazil's public health system has distributed since 2017.
The difference in how well people stuck with each approach was substantial. Among those who received injections, 94 percent showed up at their health clinic on schedule to get their shots. That consistency meant they remained protected against infection for nearly the entire study period. Not a single person in the injectable group tested positive for HIV. The oral group told a different story. Because daily pills are easy to skip or forget, people using that form were protected only 58 percent of the days they were being monitored. One person in that group contracted HIV.
When researchers compared their findings to data from about 2,400 people across 14 cities already using oral PrEP through Brazil's public health system, the picture grew more sobering. Those users achieved just 48 percent coverage—meaning they were protected less than half the time. In that larger group, nine people became infected with HIV.
The stakes matter. Brazil's most recent epidemiological report, released late last year, documented 46,495 new HIV infections in 2023, roughly 2,000 more than the year before. More than 40 percent of those cases occurred in men ages 20 to 29. Yet the country has made real progress on treatment: between 2013 and 2023, deaths from AIDS fell by nearly a third. Prevention, though, remains a challenge, particularly among young people from sexual and gender minorities.
The injectable cabotegravir received regulatory approval in Brazil in 2023 from the country's drug agency, Anvisa. Whether it will be incorporated into the public health system is still under review by the Ministry of Health, which has not announced a timeline. In a statement, the ministry acknowledged it is following the study but offered no commitment. It did note that Brazil has doubled its PrEP users in three years, reaching 119,000 people by 2025, and called PrEP—in whatever form—an essential tool for eliminating HIV as a public health crisis by 2030.
What the ImPrEP CAB study suggests is that the form the medication takes may matter as much as the medication itself. For young people juggling work, school, relationships, and the unpredictability of daily life, remembering to take a pill every single day is hard. An injection every two months is not. The research points toward a path forward, but only if the health system chooses to walk it.
Citas Notables
The injectable form is a tool with potential to address the challenges of daily oral medication adherence, particularly among younger people, and could help Brazil slow the rise of HIV cases and the disproportionate burden among young sexual and gender minorities.— Oswaldo Cruz Foundation researchers (ImPrEP CAB study)
La Conversación del Hearth Otra perspectiva de la historia
Why does the form of the medication matter so much here? It's the same drug either way.
It is the same drug, but adherence isn't about chemistry—it's about human behavior. A daily pill requires you to remember, to have it with you, to fit it into your routine every single day. An injection every eight weeks is a scheduled appointment. One is friction; the other is structure.
But couldn't someone just set a phone alarm for the daily pill?
In theory, yes. But the study tracked real people in real life, not people in a controlled trial. Life gets messy. You travel, you forget, you run out, you feel fine so you skip a day. The injection removes those decision points. You show up, you get protected for two months, you move on.
So this is really about the young people most at risk—the ones the system has struggled to reach?
Exactly. Men who have sex with men, transgender and non-binary youth in their twenties—they face disproportionate infection rates. But they also face barriers: stigma, access, trust in institutions. A medication that requires less daily effort and less daily visibility might actually reach them better.
What happens now? Does Brazil just add this to the public system?
That's the open question. The drug was approved in 2023, the study is done, the evidence is clear. But the Ministry of Health hasn't committed to anything yet. It's a resource question, a policy question, a question of political will. The science is pointing one direction; the system may move another.