HIV testing requirements must be simplified for injectable PrEP to have a future

Two slides presented at last week’s Conference on Retroviruses and Opportunistic Infections (CROI 2025) in San Francisco starkly illustrated the cost of the almost-complete defunding of HIV pre-exposure prophylaxis (PrEP) provision via PEPFAR, the US President’s Emergency Plan for AIDS Relief.

Dr Cissy Kityo, Executive Director of Uganda’s Joint Clinical Research Centre, showed that the number of people receiving PrEP at least once has expanded from one million in 2021 to eight million by mid-2024. Almost all of this growth has come from PEPFAR programmes, which now provide over 90% of PrEP globally.

In the preceding presentation, Dr Cheryl Case Johnson of the World Health Organization’s Global HIV, Hepatitis and STI Programmes showed a slide of progress towards the United Nations’ HIV targets.

Reductions in infections were already falling short of targets by the end of 2024, due partly to slower-than-intended provision of PrEP. There were 1.3 million new HIV infections in 2022 and the UN target is to bring that down to 375,000 by 2030.

However, at the current rate of decline, they will still be running at about 800,000 a year by then. Similarly, HIV-related deaths, currently at 600,000 a year, would have only declined to 400,000 rather than half that figure.

Dr Johnson then referred to a model issued recently (and not yet peer reviewed) by Dr Debra ten Brink and colleagues of the Burnet Institute in Australia.

This forecasts that if the PEPFAR cuts are fully maintained and none replaced, we should expect up to an additional 10.75 million people acquiring HIV by 2030 and up to 2.93 million more deaths. If some of the PEPFAR funding is realistically replaced or costs reduced, we might expect 4.43 million new infections by 2030 and another 770,000 deaths.

Before Donald Trump’s accession, there were hopes that the original targets might be reached after all, due to the extraordinary potential of long-acting injectable PrEP, and particularly the twice-yearly drug lenacapavir. Although this drug’s 100% efficacy in cisgender women, and 96% efficacy in gay and bisexual men and transgender women, were only announced last year, its manufacturers Gilead have signed agreements with six generic manufacturers to make an affordable version of it available by 2026-27.

At about the same time, generic versions of ViiV’s six-times-yearly PrEP drug cabotegravir should be coming online too, due to agreements signed with three generic companies.

Encouraged by these likely developments, and especially by hopes of being able to re-align with the UN targets, PEPFAR and the Global Fund announced on 17 December last year a new multi-agency initiative to provide two million people with at least one dose of lenacapavir PrEP over the next three years.

It took less than six weeks for these hopes to be dashed. Funding of PEPFAR and other US aid was slashed, and the Trump government made it quite clear that its limited waiver, allowing PEPFAR to continue funding antiretroviral therapy, did not apply to PrEP, except to prevent vertical transmission.

The US government said: “People other than pregnant and breastfeeding women who may be at high risk of HIV infection or were previously initiated on a PrEP option can not [their emphasis] be offered PEPFAR-funded PrEP during this pause of U.S. Foreign Assistance or until further notice.”

The Global Fund has pledged to uphold as much of the lenacapavir commitment as it can, according to the South African Health website Bhekisisa. The Global Fund’s Executive Director, Peter Sands, has said that “the lenacapavir commitment stands, even if the overall pledge target should not be reached… We cannot afford to miss such a game-changing opportunity.”

However, as Bhekisisa also adds, there is no guarantee the US won’t cut some or all of its Global Fund commitments, despite the Fund’s 2025 Investment Case finding that every US dollar spent on HIV, TB or malaria produces a return of $19 in health gains and economic returns.

Can we cut the cost of providing PrEP?

In the preceding presentation, Dr Cheryl Case Johnson examined why PrEP had not reached the global coverage anticipated even before the Trump administration’s cuts.

One aspect is its cost – not the cost of the drugs, which are negotiated by international bodies like PEPFAR, but the costs of providing them and especially of testing.

It is an odd aspect of PrEP that its testing requirements are more exacting than for HIV treatment, with three-monthly testing required whereas six-monthly is most frequently used for treatment.

Dr Johnson said that HIV testing recommendations had become more rather than less demanding with injectable PrEP – at least with cabotegravir – where a test is recommended at the end of the first month and then every two months afterwards.

Tests for viral RNA – the same technique used in viral load tests – can often detect an HIV infection 10 days after exposure, nearly two weeks earlier than standard HIV antibody rapid tests. In the phase III studies of injectable PrEP, retrospective testing of stored blood samples from the handful of people who tested HIV antibody positive despite receiving cabotegravir or lenacapavir found some people who were in the early days of HIV infection when they joined the study, and a few who showed signs of the so-called ‘LEVI’ (Long-acting Early Viral Inhibition) syndrome – when someone who acquires HIV despite being on PrEP has a delayed antibody response and an intermittently detectable viral load because the PrEP suppresses them.

For this reason, the two main sets of guidelines followed in the United States have been recommending HIV RNA tests when people start PrEP. For oral PrEP, they recommend that regular quarterly testing should employ the fourth-generation antibody/antigen (ab/ag) tests which detect the p24 viral protein produced early in infection and so can detect infections a week or more in advance of antibody tests.

The problem, Dr Johnson said, is that HIV RNA tests can cost US$33-$85 per test, in addition to a minimum cost of $12,000, and often much more, for the machines they run on. They also need expert lab technicians to perform the tests and interpret the results.

In contrast, rapid HIV antibody tests cost $0.50-$3.00 each and can be done virtually anywhere. Self-test kits using fingerprick blood or oral fluid cost a little more – $0.95-$5.00 each – though often have a big markup when sold in pharmacies in high-income countries.

Furthermore, RNA tests are not that reliable, especially in terms of specificity. The World Health Organization (WHO) prequalification standard is that any test must be 98% specific – meaning that for every 100 people who do not have HIV who are tested, no more than two would return a false-positive result. In a setting of low HIV incidence, where, by definition, true positive tests are rare, most positive results from any testing modality will be false and, if using RNA tests, expensive, needing to be performed twice for confirmation.

Expecting RNA tests to be used in lower-income settings is simply unrealistic, Johnson said. Only one of the currently marketed RNA tests actually has an indication for HIV diagnosis, as opposed to viral load of people living with HIV, and 95% of all HIV testing worldwide is done at health centres and in the community with standard rapid tests.

Dr Johnson cited a study by Dr Sara Cox and colleagues of the University of Washington, who modelled how many people in a population of 3.7 million heterosexual Kenyan PrEP users might start PrEP inappropriately because they already unknowingly had HIV – whether the diagnostic tests used were RNA tests, standard rapid antibody tests, fingerprick blood self-tests, or oral fluid self-tests. They modelled the results both for people who were recently infected with HIV and people who had had it for some time.

They found that if RNA tests were used as the standard diagnostic test, 1312 people who had recently acquired HIV might start PrEP inappropriately. If standard rapid HIV tests were used, the number would be 2214. And if self-testing using oral fluid was used, with realistic adherence, 5650 people might start PrEP while HIV positive. If people had had HIV for some time, then RNA testing would correctly diagnose most of them, so almost no people would be wrongly put on PrEP. But with oral self-testing, as many as 11,942 people starting PrEP might do so already having HIV.

The problem with starting PrEP when antiretroviral therapy (ART) should be taken instead is that because PrEP lacks that one crucial extra drug, people with HIV on PrEP may develop drug resistance.

In the model, 433 people with acute HIV infection might start PrEP inappropriately and get drug resistance if RNA tests were used, and 1865 people if oral self-tests were used. But the model doesn’t distinguish between people who might get resistance to emtricitabine (common, but unlikely to impact on future treatment choices) or the injectable drugs (less common but may restrict which drugs work in future).

Overall, Dr Johnson said, missed cases due to not using RNA testing were few – 0.18% of PrEP users. This implies that to detect one additional HIV case using RNA testing, that was missed by a standard rapid test, would require testing 5305 people, at an estimated cost ranging from $47,000 to $450,000.

These figures have been sufficient to convince WHO that which HIV test was used makes no substantial difference in drug resistance at a population-level, and no difference to the overall number of HIV-deaths or infections averted.

As a result, WHO is planning to reaffirm the use of standard rapid tests for PrEP, including for injectable PrEP. Also, self-testing should be brought forward as an option.

Many sites in Africa are coming round to using two rapid tests as the best combination or reliability and affordability. And several PrEP studies in Africa and Brazil are evaluating self-testing, even in the context of cabotegravir injections.

Even in high-income countries, the feasibility of RNA testing is questionable and the funding outlook is increasingly uncertain. Already, one set of guidelines widely followed in the US has been changed. The International Antiviral Society (IAS-USA) now says that although RNA testing is still best for initiating PrEP, where it is unavailable they recommend initiating PrEP after a standard rapid test, using an ag/ab test for confirmation.

Dr Johnson quoted several PrEP users from around the world who had included self-testing as part of their PrEP regimen, including a young Thai man, Pangpond, who said:

“It was so simple. The clinic sent me the HIVST kit. I had to ask the clinic for advice online when I first used it, then I sent them the result, and they sent me PrEP to initiate. This was incredibly convenient, and I quickly regained control, feeling ready to enjoy life again.”