The effect of introduction of universal childhood hepatitis B immunizationin South Africa on the prevalence of serologically negative hepatitis B virus infection and the selection of immune escape variants

The effect of universal hepatitis B vaccination on the prevalence of serolo gically negative hepatitis B virus infection (HBV) and the emergence of HBs Ag variants is unknown. We prospectively studied two different cohorts of 1 2-24 month old children in South Africa. They consisted of the unvaccinated children (n = 459) born before the introduction of universal vaccination a nd the vaccinated children (n = 1213) between 1 and 2 years after the intro duction of the vaccination program. The frequency of detecting HBV DNA by P CR was reduced from 6.5% in unvaccinated children to 0.3% in vaccinated chi ldren (P < 0.00001). There were no unique amino acid substitutions within t he major hydrophilic region of the S sequence in both pre- and post-vaccina tion samples. Universal childhood vaccination reduced the frequency of sero logically negative HBV infection and did not necessarily lead to selection of escape variants. (C) 2001 Elsevier Science Ltd. All rights reserved.