The effects of booster vaccination on combined hepatitis A and hepatitis B vaccine in both anti-HBs and anti-HAV negative children 5–15 y after hepatitis B vaccine primary immunization

In the present study, we investigated the changes in both anti-HAV lgG and anti-HBs lgG levels and compared the antibody seroconversion rates of different doses of combined hepatitis A and hepatitis B vaccine in children. Children who were vaccinated as infants with Hepatitis B vaccine were revaccinated at 5-15 y of age, then the antibody titers were monitored. Among 283 children, this study found that the anti-HAV seroconversion rates (defined as anti-HAV ≥ 1 mIU/ml) after the first and the third dose were 79.9% and 100% respectively; these observed differences were statistically significant (P<0.05); the corresponding geometric mean titers (GMTs) were 4.72 ± 2.63 mIU/ml and 13.46 ± 1.16 mIU/ml respectively. The anti-HBs seroconversion rates (defined as an anti-HBs ≥ 10 mIU/ml) were 82.3% and 99.0% respectively; these observed differences were statistically significant (P<0.05); and the corresponding titers were 319.95 ± 5.16 mIU/ml and 418.59 ± 3.89 mIU/ml respectively. After the first booster dose, the difference in anti-HAV seroconversion rate was statistically significant in children aged 5-9 y and 10-15 y (P<0.05), as was the difference of anti-HBs seroconversion, whereas after the third dose the difference was not statistically significant (P>0.05). This study demonstrated that the immunization effects of booster vaccination with combined hepatitis A and hepatitis B vaccine is successful for children. A single booster dose is adequate for younger children, while three doses are needed for older children.