Background Pre-exposure prophylaxis (PrEP) is highly protective against sexual acquisition of HIV among men having sex with men (MSM). The cost-effectiveness of PrEP will play a major role in deciding whether the NHS should introduce PrEP.

Aim To evaluate the cost-effectiveness of introducing PrEP among MSM in the UK.

Methods An individual-based dynamic stochastic model calibrated to the HIV epidemic among MSM in the UK was used. It was assumed that, from 2016, 50% of people who tested negative for HIV and who had periods of condomless sex with a long-term or casual partners would use PrEP during such periods. While on PrEP men would be tested three-monthly and PrEP discontinued if diagnosed HIV-positive or if not engaging in condomless sex for that three-month period (and restarting PrEP if again engaging in condomless sex).

Results Preliminary results indicate that the introduction of PrEP would lead to a gain in quality-adjusted life years. If current costs of antiretrovirals and PrEP are assumed for the next 30 years (as is generally regarded as good practice in the base cases analysis) PrEP introduction is not cost-effective. However, when considering likely reductions in costs of antiretrovirals and PrEP, due to the use of generic drugs, PrEP would likely be cost-effective.

Conclusion Our preliminary evaluation suggests that the use of PrEP for MSM during periods of condomless sex is not cost effective at current antiretroviral prices, but it would become cost-effective if drug prices are reduced after patent expiry date.