Abstract Body

In the UK, HIV incidence among gay and bisexual men (GBM) has decreased substantially. Our aim was to understand the contribution to this of the different components of combination prevention, and to estimate the impact on HIV incidence going forward of continuation of current policies.

We calibrated a dynamic, individual-based stochastic model, the HIV Synthesis Model, to multiple sources of data on HIV among GBM in the UK. We compared HIV incidence in 2020 with the counter-factual incidence if: (1) from 2013 condom use was low, i.e. at levels similar to those observed in 1980; (2) the HIV testing rate had remained stable from 2013; (3) the policy of antiretroviral treatment (ART) at diagnosis (as opposed to CD4 count < 350/mm3) was not introduced in 2015, and (4) a Pre-exposure Prophylaxis (PrEP) strategy had not been introduced (through the PROUD and IMPACT trials, self-sourcing, and lately commissioning) with consequent lower levels of testing (recommended three monthly on PrEP) and ART initiation. We also projected future outcomes under the assumption of continuation of current policies.

The intervention that had the biggest impact on HIV incidence by 2020 was PrEP, followed by ART at diagnosis. If either of these had not been introduced (but other interventions had been as implemented), HIV incidence in GBM in 2020 would have been respectively 52% and 22% higher than estimated in the scenario with the implementation of all components of combination prevention. Our results suggest that the HIV epidemic among GBM in the UK is on course to eliminate HIV with an incidence rate of 1.7/1,000 person-years in GBM aged 15-64 (90% range: 0.6 – 4.8/1,000 person-years) in 2020, declining to 0.55 (90% range: 0.25 -1.3) per 1,000 person-years in 2030 and to 0.23 (90% range: 0.11 – 0.54) per 1,000 person-years by 2040.

Since 2013, combination prevention, including widespread availability of PrEP, played a major role in the reduction in HIV incidence observed in the UK among GBM. Continuation of current prevention policies should lead to HIV elimination among GBM in the UK.