HBV is transmitted via exposure to infected blood and body fluids, with infection occurring via vertical (perinatal infection from mother to child), sexual, parental or percutaneous routes. 5-10% of people with HIV infection are co-infected with HBV, with long-term sequalae such as cirrhosis and hepatocellular carcinoma occurring with increased frequency in co-infected patients (9). HBV vaccine is recommended for HIV patients with no immunity to HBV (HBsAg negative, HBsAb <10 IU/ml), especially in those with risk factors for acquisition.
HBV vaccine contains a recombinant virus protein so can be given at any CD4+ T cell count. There is no evidence that people with HIV infection have a higher rate of adverse events following administration of HBV vaccine compared with individuals not infected with HIV. However response rates to vaccination vary widely with reduced response rates (as low as 33%) associated with low CD4+ T cell counts and high HIV viral load at the time of vaccination (10-12). Given this information, it may be reasonable to delay vaccination in non-immune individuals or delay re-vaccination in non-responders until HIV replication is suppressed by ART and the CD4+ T cell count is >200-350 /m L.
A meta-analysis of 5 studies concluded that high dose HBV vaccine (40mg) provided higher HBV surface antibody (HBsAb) response rates compared with standard dose vaccine (20mg) with a pooled OR of 1.96 (95% CI 1.47-2.61) (13). In a multicentre randomised controlled trial, four doses of high dose (40mg) vaccine at intervals of 0, 1, 2 and 6 months was associated with superior seroconversion (82%) compared with three standard dose (20mg) vaccines at 0, 1 and 6 months (65%) (7). However an alternative strategy of three high dose vaccines at 0, 1 and 6 months with an additional 4th dose of 40mg if seroconversion (HBsAb>10 IU/L) has not occurred is a feasible alternative, with a retrospective study revealing three high dose vaccines efficacious in 83% of patients (14). Regardless of whether using the 3 or 4 dose strategy, clinicians should check HBsAb 4-8 weeks after the last dose and repeat dosing (1 further dose if 3 initial vaccines given, or repeat full course if 4 initial vaccines given) if HBsAb <10 IU/L.