Introduction To inform public health planning for a large-scale PrEP trial in England, we estimated the need for HIV pre-exposure prophylaxis (PrEP) among men who have sex with men (MSM) attending sexual health clinics.

Methods National STI surveillance data from the genitourinary medicine clinic activity dataset (GUMCADv2) were used to estimate the annual number of HIV-negative MSM who had a HIV test in the past year (which will be a criterion for accessing PrEP in England), for 2010–2015. To estimate the number and proportion of all MSM needing PrEP, we used bacterial STI diagnosis in the past year as a proxy for high-risk behaviour, and estimated HIV incidence (per 100 person-years) in both groups. We used these data to understand the likely geographical distribution of MSM who might need PrEP within the 152 English counties.

Results The number of HIV-negative MSM attending sexual health clinics increased by 68% from 69 392 in 2010 to 1 16 546 in 2015, and the number of HIV-negative MSM with a prior HIV test nearly doubled from 14 643 to 29 023 in the same period. Among HIV-negative MSM with a prior HIV test, the number with a recorded bacterial STI (past year) increased from 4365 (30%) in 2010 to 10,276 (35%) in 2015 (33% on average). HIV incidence among MSM with a prior HIV test was 1.9 (95% CI 1.6–2.2) per 100py compared to 3.3 (2.7–4.0) per 100py in MSM with a prior HIV test and history of bacterial STI. The number of MSM in need of PrEP (according to bacterial STI history) was 200 men in 4% (6/152) of counties.

Conclusion We estimated that the need for PrEP among MSM in England in 2015 might be around 10 000 individuals with an annual HIV incidence of 3%. Need for PrEP was highly concentrated; in most English counties, the number of MSM with a prior HIV test was small, and only 33% of these men might be clinically assessed as eligible for PrEP. These data illustrate how the population need for PrEP might be estimated in advance of a national trial, and will inform future evaluations at a population level.