Immunogenicity of low-dose and conventional-dose recombinant hepatitis B vaccines in healthy adolescents in India.
The recombinant hepatitis B vaccine, at a conventional dose of 20 microgrammes, is highly effective in a majority of the population. Recent studies have reported that a 10-microgramme dose is as effective as the conventional dose, especially in young adolescents. This study compares the effect of two different doses of recombinant hepatitis B vaccine (Enivac HB) in healthy adolescents. Ninety-two adolescents were randomised into two equal groups to receive either 10 microgrammes (group 1) or 20 microgrammes (group 2) of vaccine using the vaccination schedule of 0, one and six months. Blood samples were collected at 30, 60, 90, 180 and 210 days to detect anti-HBs antibodies. At each interval, geometric mean titres were calculated for seroconverted subjects. After the initial doses of the vaccine, greater proportion of subjects receiving the higher dose seroconverted. However, at six months, all subjects who received the low dose seroconverted, as did those who received the conventional dose. Furthermore, there were significant differences in the anti-HBs geometric mean titres for seroconverters at 180 days (218.27 versus 111.43) and 210 days (345.14 versus 133.35). The difference in the overall reactogenicity for the two dose levels was not remarkable, although the higher dose produced more local symptoms. 10-microgramme recombinant vaccine can be used in routine immunisation in healthy adolescents. If quick immunisation is needed, as in high-risk groups, the conventional dose should be administered, as it results in earlier seroconversion with higher anti-HBs geometric mean titres.