Immunogenicity of low doses of hepatitis B vaccine in normal children.

The immunogenicity of two low doses (5 micrograms and 10 micrograms ml-1) of hepatitis B vaccine was tested in 98 non-immune children. The seroconversion rate after the third dose was 100%. High seroconversion rates were observed even after the first dose as well as progressive increase in the geometric mean titres of the converters after each dose. The geometric mean titre in International Units one month after the third dose was higher (18 276 mIU ml-1) in children vaccinated with 10 micrograms ml-1, compared to children vaccinated with 5 micrograms ml-1 (11 313 mIU ml-1). The lowest seroconversion rate after the first and second doses and the lowest final mean geometric titre was observed in children aged 11-15 years.