Introduction Hepatitis A infection in MSM increased in incidence from late 2016 in the UK and has reached outbreak status. By February 2017, 42 confirmed or suspected cases had been reported in London. BASHH hepatitis guidelines recommend HAV vaccination of MSM in outbreak situations.

Methods We looked at 100 consecutive MSM who attended our service for the first time in early 2016 to assess what the vaccination needs of MSM would be.

Results Sixty seven of these MSM had a baseline HAV total antibody test of which 33 (49%) were HAV-Ab positive. A further 5/66 (8%) MSM gave a history of HAV vaccination but were antibody negative. 16/33 (48%) HAV-immune MSM gave a history of previous vaccination. 7/66 (11%) of the MSM who were immune, but non-vaccinated, came from HAV-endemic countries and presumed naturally immune.

49/98 (50%) who had baseline HBV antibody levels were HBV-immune of whom 14/49 (29%) were also HAV immune.

Extrapolating from these data, our estimates for baseline vaccination requirements in new MSM were: 28% require monovalent HAV vaccine, 24% require monovalent HBV vaccine, 21% require bivalent HAV/HBV vaccine and 27% require no vaccine.

Discussion If these data are representative of MSM in London, 49% (57% including those vaccinated but HAV-Ab –ve) are already HAV-immune. This has implications with regards to estimating the pool of non-immune MSM at-risk. It also enables us to estimate the types of vaccine required to meet the MSM’s needs in relation to HAV as well as HBV in the current outbreak