A model of the likely efficacy and cost-effectiveness of PrEP in 15 Asian countries plus Australia finds that long-acting injectable PrEP using the drug cabotegravir, if based on patterns of preference and usage established in a previous study, would reduce the number of HIV infections in gay and bisexual men by at least 50% more than oral PrEP.
Crucially though, it also finds that cabotegravir injections would be unaffordable in terms of the cost per HIV infection averted if they are only discounted, compared to the US price, by the same amount as oral PrEP currently is.
Oral PrEP, in contrast, would likely be cost-saving or nearly so, in terms of the cost per disability-adjusted-life-year (DALY), in all five higher income countries studied except for Japan. In middle-income countries the cost even of daily oral PrEP per DALY would tend to exceed cost-effectiveness thresholds at current, commercially available, prices.
However, on-demand PrEP is expected to be as effective as daily oral PrEP, while being considerably more affordable. This would bring the cost-effectiveness nearer to what most countries can afford, and the authors say that policy makers need to consider the “economic efficiency” of on-demand PrEP.
The study also modelled PrEP efficacy and cost in transgender women in the 11 countries defined as middle-income, with roughly similar results; data were not available for trans women in the five high-income countries.
The model is based upon the PrEP APPEAL survey. This was a large survey conducted among gay and bisexual men in 15 Asian countries plus Australia in May 2022 and among transgender women in 11 countries in November 2022, via dating apps and community organisations.
The study was conducted by the China-Australia Joint Research Centre for Infectious Diseases, a collaboration between Xi’an and Monash Universities. Participants came from Australia, Hong Kong, Japan, Singapore and Taiwan (the high-income countries) and Cambodia, mainland China, India, Indonesia, Laos, Malaysia, Myanmar, Nepal, Philippines, Thailand and Vietnam (the middle-income ones).
The ‘PrEP cascade’ among study participants, and their preferences for how to receive PrEP, have already been published in two other papers. For the ‘PrEP cascade’ analysis, Australian participants were excluded and there were 13,899 participants with enough data for analysis. Of these, 11,427 people were aware of PrEP (83%), with highest awareness in Taiwan (96%) and lowest in Laos (50%). Of those aware, 4000 had ever used PrEP (35% of those aware, 29% of all surveyed) and 2803 were currently using it (70% of those who had ever used it, 20% of all surveyed). The highest proportions who had ever used PrEP and were currently using it were in Nepal, where 54% of all surveyed were currently using it. The lowest proportion of current users was in India (4%), though the highest proportion who had ever used PrEP, but were not currently doing so, was in Laos.
The study also asked participants who had not used PrEP whether they would be willing to use it. Of the 7472 in this category, 4068 (55%) were defined by the researchers as being at “substantial risk” of HIV. Substantial risk meant that a participant reported, in the previous six months, more than ten anal sex partners, condomless anal sex (regardless of the number of partners) or an STI diagnosis. Of the 4068, 74% of participants at higher HIV risk or 40% of all PrEP-naïve participants were willing to use PrEP. Those willing were also asked if they would be willing to pay for PrEP; on average, 74% would be, though this correlated with the average GDP in their country.
The second analysis reported on preferences. It involved 21,943 gay and bisexual men and 1522 trans women, and did not exclude the Australians. It asked participants to rank their preferences for type of PrEP (daily oral, on-demand oral, long-acting oral, injections, and implants); cost (from free to substantial); how PrEP is accessed (hospital, STI clinic, private clinic including GP, community-run clinic, online or phone, pharmacy), risk of side effects, frequency of appointments, and other services offered.
Overall, 50% more participants said they would use PrEP if it combined the most favoured options (free, at a community-run clinic that also offered STI testing, and with appointments every 6-12 months) than the least-favoured (substantial cost, implant, some risk of kidney problems and appointments every two months). Low or no cost was universally preferred, and an implant almost unanimously seen as the worst option.
In contrast to some other preference studies, oral PrEP was far more popular than injected, with preference in gay and bisexual men split between on-demand (the most popular type in eight out of 16 countries) and an – as yet unavailable – long-acting oral pill (the most popular in six out of 16). The trans women preferred a long-acting injection.
All this data formed some of the input to the population-impact and cost-effectiveness model, which asked if PrEP was more widely available and was used by all the interested people as well as current users, how many HIV infections would it stop – and at what cost?
The likely prevention efficacy of PrEP was calculated by estimating incidence in each population and calculating the reduction in the annual number of HIV infections if usage was as documented and predicted in the cascade study. Based on a number of studies and meta-analyses, the authors estimated 75% effectiveness for oral PrEP and for injectable PrEP, 94%.
Note that because only 20% of participants were current users and 40% interested in starting or re-starting PrEP, this model incorporates an assumption that 40% of the population who might benefit from PrEP would not use it.
The type of PrEP used was divided into daily oral, oral on-demand, long-acting injectable, or mixed-modality: the latter was based on the likely patterns of usage predicted by the preferences study, but excluding implants and long-acting oral, which are not yet available.
The hardest variable to incorporate in the model was cost. What health systems actually pay for PrEP varies by more than three orders of magnitude, depending on prices international donors and local health systems have secured. The study authors did not assume the very lowest costs, and have noted that in many middle-income countries “PrEP has been provided at a heavily subsidised price, enabled by external donor funding…. However, this model faces major challenges when funding ceases or transitions to the national health system.”
Accordingly, for oral PrEP, they used the local advertised price for the most widely-used generic emtricitabine/tenofovir disoproxil (FTC/TDF) pill, Cipla’s Tenvir-em. Prices for daily oral PrEP ranged from $619 per year in Japan to $41 in Cambodia, with on-demand PrEP costing about half of that, as they supposed that it would involve taking an average of 16 pills per month.
For injectable cabotegravir, they faced the fact that there is as yet no agreed price for it in most countries. PEPFAR negotiated a price of $180 a year in 2024 but this has been thrown into uncertainty since the Trump government cut the majority of PEPFAR-supported programmes. In the US, the list price of cabotegravir injections is $22,200 a year and the UK has negotiated a discounted price of about $9640.
Reluctant to plug either the lowest or highest possible price into their model, the authors instead estimated the likely discount for cabotegravir per country by comparing the US list price for the original PrEP pill, Truvada ($17,045), with its locally available price in the 165 countries, and then applying the same discount ratio to cabotegravir. (The reason they used Truvada rather than Tenvir-em is because in most middle-income countries, the price for Truvada was in fact lower). This resulted in estimates of the likely annual price of cabotegravir ranging from $15,738 in Hong Kong to $477 in India, with an average price in high-income countries of $8815 and in middle-income countries of $1979, compared to $461 and $197 respectively for oral PrEP.
For gay men in high income countries with substantial risk of HIV, if injected cabotegravir became the sole method of PrEP and usage was in line with the PrEP APPEAL study, we would expect to see 28% fewer HIV acquisitions a year than are seen currently. If ‘mixed modality’ PrEP, in line with individual preferences, became the norm, then the average reduction in new HIV acquisitions would be slightly lower, at about 26%.
If oral PrEP continued to be the norm, then we would see an 18% reduction in new HIV infections in these countries. There would be almost no difference in impact whether daily or on-demand PrEP was used. In gay men at lower risk of HIV, injectable PrEP would be almost as effective as in higher-risk men but oral PrEP slightly less so.
In middle-income countries, PrEP would generally be rather less effective than in high-income countries, because of projected lower levels of use. In gay men at higher risk, 18% of new infections would be prevented by injectable PrEP and 14% by oral PrEP. Interestingly, rather more infections would be prevented in lower-risk gay men in these countries (22% for injected and 15% for oral), possibly because of lack of prior PrEP use.
In trans women, there would be 23% fewer acquisitions in a year if injectable PrEP was fully adopted, and 13% fewer if oral PrEP (daily or on-demand) was solely used. Mixed-modality PrEP would prevent 22%.
Firstly, the researchers calculated the cost of PrEP averting one HIV infection in the 16 countries.
They did this by comparing their current estimates of the number of HIV acquisitions with what the number would be, taking into account efficacy and preferences, if one of the four methods of PrEP was fully adopted.
This results in what looks like unsustainable expense. For instance, in the higher income countries the cost per infection averted of the cheapest form of PrEP – on-demand oral – among gay and bisexual men at substantial HIV risk varies from over $34,000 in Taiwan to $225,247 in Japan. The equivalent figures for injectable cabotegravir are $460,468 and $3,080,640.
In middle-income countries, costs per infection averted for the same population are more variable. For on-demand oral PrEP, they range from $4641 in Vietnam to $108,847 in mainland China, although this is an outlier – the cost is $21,541 in the second most expensive country, Malaysia. For cabotegravir injections, the cost per HIV acquisition averted is again the highest in mainland China at $747,816 and the cheapest in India at $37,284.
Although the cost of preventing one HIV acquisition is the main cost-effectiveness metric used in the main part of the paper, most cost-effectiveness studies use a different measure – the cost in disability-adjusted life years (DALYs). When PrEP methods are measured against DALYs, PrEP can become much more cost-effective.
Measuring infections averted essentially looks at the past and asks: if we had implemented this measure, instead of doing nothing, how many other infections would we have prevented, and what would that have cost?
Measuring DALYs looks more into the future and asks: if we implement this measure, how many years of life with impaired health can we prevent? And what is the cost of doing so? Whereas the cost of an HIV infection is counted as a single sum, DALYs are an annual cost, meaning they save more money per extra year of healthy life.
Researchers can estimate QALYs (Quality-Adjusted Life Years) gained, which evaluates the intervention against life expectancy in good health. But they evaluate the number of DALYs averted, in other words: what cost to the healthcare system in terms of caring for people who acquire a ‘disability’ (in this case, HIV) can we avoid if they take PrEP?
Because the costs of treating HIV are so much more in high-income countries, measuring cost-effectiveness per DALY averted makes a bigger difference. In Hong Kong and Taiwan, daily or on-demand oral PrEP becomes cost-saving – the healthcare system will (eventually) save money if everyone who wants it, starts it. In Singapore, on-demand PrEP becomes cost-saving and daily probably so, and in Australia, it is more likely to save money than cost it (within the statistical uncertainty of the model). Only in Japan would daily oral PrEP still cost money per DALY averted – about $25,000 – but on-demand PrEP would still save money.
What about cabotegravir injections? Because of its considerably greater cost, they remain unaffordable, with costs of over $100,000 per DALY averted. However, ‘mixed modality’ PrEP becomes affordable, at $6047 per DALY averted, in Taiwan.
There is less benefit in counting cost-effectiveness in DALYs in middle-income countries, because the life costs of treating HIV are generally lower, relative to the cost of PrEP. On-demand oral PrEP becomes cost-saving in Vietnam and probably in Myanmar, and daily probably becomes cost-saving in Vietnam, but in Malaysia daily PrEP still costs around $10,000 per DALY averted and on-demand PrEP $5,500. In mainland China, because the cost of PrEP in the model is relatively high compared with the cost of HIV treatment, even on-demand PrEP would still cost around $40,000 per DALY averted.
Injectable cabotegravir is still out of reach for gay and bisexual men. But because injectable PrEP was somewhat more popular among transgender women, ‘mixed modality’ PrEP approaches affordability in Indonesia ($2762 per DALY averted), India and Vietnam (both about $3800).
Human immunodeficiency virus, the virus which causes AIDS. There are two variants: HIV-1, and HIV-2. HIV-1 is by far the most common worldwide. See ‘subtype’ for more information.
Abbreviation of a Latin term meaning every night.
In relation to pre-exposure prophylaxis (PrEP), on-demand dosing is an alternative term for event-based dosing. See ‘event based’.
Refers to the mouth, for example a medicine taken by mouth.
What if injectable PrEP could be made cheaper? The authors applied a ‘sensitivity analysis’ to their model that supposed that injectable PrEP became available for $40 a year for middle-income countries and $221 for higher-income countries.
This increases the number of countries for whom injectable PrEP is affordable, but not for all. In the higher-income countries injectable PrEP becomes cost-saving for men at substantial risk of HIV, as it is in Myanmar, Vietnam and the Philippines. For transgender women, generic lenacapavir is cost-saving for India, Indonesia, Myanmar, Vietnam and the Philippines.
But this still leaves countries where the cost of injectable PrEP, even with generic lenacapavir, costs over $1000 per infection averted, namely Thailand, Malaysia, Cambodia, mainland China and (for gay men) India.
As for the cost per year per HIV acquisition averted, either 100% injectable or mixed-modality PrEP, or both, come in at under $10,000 for most middle-income countries except Cambodia and mainland China. However, for high-income countries, because it is still a more expensive option, its cost per HIV acquisition averted – as opposed to DALYs averted – is still in the tens to hundreds of thousands of dollars.
As can be inferred from this report, this was a complex modelling study with numerous and diverse inputs. However, because it based its forecasts on the likely uptake of PrEP among its target population, rather than on supposing that everyone who needs PrEP will take it, its conclusions may be more realistic.
The models, as all models do, includes some assumptions – such as the likely price of cabotegravir and the likely background infection rate of HIV – that produce very different results if adjusted.
The authors note that “implementing preference-driven PrEP strategies, particularly for long-acting injectable PrEP, could substantially reduce annual HIV acquisitions” in the countries studied.
“However,” they add, “a dilemma exists between the superior effectiveness of high-cost long-acting injectable PrEP and the economic efficiency of on-demand PrEP. Future strategies should incorporate diverse modalities aligned with preferences… [and] prioritise resources for the populations at substantial risk.”
He SH et al. Epidemiological and economic effect of preference-driven HIV pre-exposure prophylaxis implementation for men who have sex with men and transgender women across 16 countries and territories in the Asia–Pacific region: a modelling study. Lancet HIV 13: e478-489, 2026.
DOI: 10.1016/S2352-3018(26)00053-6
Also see:
Wirawan GBS et al. PrEP use and willingness cascades among GBMSM in 15 Asian countries/territories: an analysis of the PrEP APPEAL survey. Journal of the International AIDS Society 28: e26438, 2025 (open access).
https://doi.org/10.1002/jia2.26438
Tieosapjaroen W et al. Preferences for HIV pre-exposure prophylaxis among men who have sex with men and trans women in 15 countries and territories in Asia and Australia: a discrete choice experiment. Journal of the International AIDS Society 28: e70025, 2025 (open access).
