P3.122* Hepatitis B Incidence 2002–2012 and Falling Levels of Immunity in Men Who Have Sex with Men (MSM) at Sexual Health Service, Melbourne

Abstract

Background: Incidence of hepatitis B has not been well studied in men who have sex with men (MSM) recently despite increases in sexual risk practises and sexually transmitted infections (STI). We determined the level of immunity to hepatitis B and the incidence of hepatitis B infection among MSM attending a sexual health service during last 10 years. Methods: The study involved a cross sectional analysis of all MSM attending Melbourne Sexual Health Centre (MSHC) during 1st July 2002 - 30th June 2012 and a retrospective cohort study of MSM who had attended MSHC on multiple occasions and had hepatitis serology done more than once. Results: Of 10031 MSM attending MSHC, 58% (95% CI 57.4%-59.4%) (5655/9677) had hepatitis B surface antibody (HepBsAb), 11% (95% CI 10.0%-11.4%) (840/7888) had core antibody (HepBcAb) and 4% (95% CI 3.0%-4.5%) (95/2577) had surface antigen (HepBsAg). The proportion decreased, with HepBsAb from 72% to 48% [P (trend) < 0.001], with HepBcAb from 12% - 8% [P (trend) = 0.039] and with either HepBsAb or HepBcAb, from 67% - 50% [P (trend) < 0.001] from 2002 to 2012 but no change for HepBsAg [P (trend) = 0.08]. Later year (2007-12) of being tested (adjusted odds ratio (AOR) 0.65, 95% confidence intervals(CI) 0.58-0.73), more partners in last 12 months (AOR 1.19, 95% CI 1.06-1.34) and previous HIV test being performed (AOR 1.63, 95% CI 1.43-1.81) were associated with immunity to hepatitis B. There incidence rate of hepatitis B (7 cases in 3540 per years of observation) in MSM over the period was 1.98 (95% CI 0.79 - 4.07) per 1,000 person years. Conclusion: The data suggest that the current level of immunity of about 50% has been sufficient to prevent any significant hepatitis B infection in the last 10 years. Maintaining adequate vaccination levels (= 50%) in MSM is important if outbreaks are to be prevented