Background HIV and hepatitis B virus (HBV) share transmission modes. HIV infected people are thought to be at increased risk of HBV acquisition, chronic HBV infection and HBV disease. Chronic HBV infection may pose a challenge among HIV infected individuals' eligible for antiretroviral therapy, increasing their risk of rapid HIV-disease progression. Early prevention of HBV infection by vaccinating HIV infected people is recommended. However, in most poor countries HBV vaccination is not routine and those opting for vaccination are rarely tested before vaccination. We sought to determine the prevalence of HBV infection and natural immunity against HBV infection among HIV discordant couples.

Methods The first 949 discordant heterosexual couples screened for eligibility into an HIV pre-exposure prophylaxis study had HBV surface antigen (HBsAg) and anti-HBs status determined. CD4 count was also performed for HIV infected potential subjects. None of these participants reported HBV vaccination history. SPSS version 17 software was used for statistical analysis.

Results Of 949 HIV positive subjects, 34.7% (329) were men thus women were more likely to be the HIV-positive spouse in these HIV-discordant relationships (p<0.001). 99 of 1898 subjects were positive for HBVsAg, resulting to 5.2% HBV prevalence, with men being more likely to be HBV infected compared to women (p<0.05). 40% (758) of 1898 subjects tested for anti-HBs were immune to HBV, with men being more likely to possess natural protective antibodies against HBV compared to women (p<0.05). Among HIV infected subjects, those with a CD4 count >250 cells/ml were more likely to possess immunity against HBV compared to those with a CD4 count <250 cells/ml (p<0.001). However, HIV status was not associated with either HBV infection (p=0.302) or immunity against HBV (p=0.512).

Conclusion Scaling-up routine vaccination after anti-HBs screening in resource limited settings could be cost-effective and easy to roll-out in HIV endemic Sab-Sahara Africa. This is because 40% of individuals are already immune to HBV. Validation of Anti-HBs rapid screening tests is urgently needed in this population.