Abstract
BACKGROUND & AIMS: The standard regimen of hepatitis B vaccination, i.e., three doses at 0, 1, and 6 months, protects 90-95% of vaccine recipients. Compliance for three doses, administered over six months, is particularly low among people who inject drugs (PWIDs). To prevent hepatitis B virus (HBV) infection, the World Health Organization has recommend to vaccinate PWIDs with an accelerated regimen, i.e., in a 0-, 7-, and 21-day schedule. We compared the serological immune response with standard and accelerated vaccination regimens in PWIDs. METHODS: PWIDs were vaccinated with three doses of hepatitis B vaccine as a part of routine preventive services in the past, which was not the part of our research work. Each of them had taken a conscious and informed decision to choose either the standard or accelerated regimen at the time of vaccination. For this cross-sectional observational study, anti-HBs (anti-HBs) titers were measured in vaccine recipients at ≥3 months after the administration of the third dose of vaccine. Vaccine-induced seroconversion was defined as presence of detectable anti-HBs titer, and seroprotection was defined as anti-HBs titer measuring ≥10 mIU/mL. Numerical and categorical data are expressed as median (interquartile range) and percentage (proportion), respectively; groups were compared using nonparametric tests. RESULTS: The study included 567 PWIDs (all men; age: 29 [24-38] years) vaccinated with either the accelerated (n = 356; 62.8%) or standard (n = 211; 37.2%) regimen. Participants' ages were comparable (P = 0.99) in accelerated (29 [24-38.5] years) and standard (29 [24-37] years) groups. The interval between the last dose of vaccine and anti-HBs titer estimation was significantly longer in the accelerated group (487 [422-625]) than in the standard group (176 [105-211] days) (P < 0.001). A higher proportion achieved seroconversion in the standard group than in the accelerated group (99.5% vs 91.9%; P < 0.001). Among those who achieved seroconversion, a larger proportion in the standard group were seroprotected than in the accelerated group (99.5% vs. 92.1%; P < 0.001). Anti-HBs titer was significantly higher in the standard group (2404 [412-12450] mIU/mL) than in the accelerated group (247 [57-1250] mIU/mL) (P < 0.001). CONCLUSIONS: Accelerated regimen of hepatitis B vaccination is well accepted among PWIDs and provides seroprotection to a large proportion of vaccine recipients, though the vaccine-induced antibody titers remain relatively lower. For high-risk groups such as PWIDs and other mobile population groups, an accelerated vaccination regimen may be a reasonable alternative to the standard vaccination schedule.