by Gus Cairns

A retrospective cohort study of gay and bisexual men attending sexual health clinics in Japan shows that taking HIV pre-exposure prophylaxis (PrEP) not only protects against HIV but also against infection with hepatitis B, reducing the risk of it nearly tenfold. The study was presented at the Conference on Retroviruses and Opportunistic Infections (CROI 2020).

This is a considerably greater risk reduction than that provided by getting vaccinated against hepatitis B. However, the researchers emphasised that hepatitis B vaccination was still important for people at risk as it prevented half of infections and even when it did not prevent infection, it reduced hepatitis B symptoms to almost nothing.

PrEP involves two antiretroviral drugs: tenofovir disoproxil fumarate and emtricitabine, both of which are active against HIV and also hepatitis B. A previous study in Japan had found that people with HIV who were prescribed either tenofovir or lamivudine – usually both – as part of their antiretroviral therapy (ART) had one-tenth of the risk of hepatitis B infection than people not on ART, and one-eighth of the risk of those taking ART that did not feature either of those drugs (see also this Dutch study).