Evidence for a change in the epidemiology of hepatitis B virus infection after nearly two decades of universal hepatitis B vaccination in South Africa

Abstract

The hepatitis B vaccine has been part of the South African Expanded Program on Immunization since April 1995 but its long-term impact remains unknown. This study tested 1,206 sera collected from patients aged 1-25 years from various health facilities across the country for HBV serological markers and HBV DNA. Based on the year the vaccine was introduced, samples were stratified by age into pre- and post-vaccine introduction populations, which were then compared for evidence of immunity and chronic carriage using the Chi-square test. Where HIV status was known, subset analyses were performed. Immunity to HBV infection increased from 13.0% in the pre- to 57.0% in the post-vaccine introduction population (P < 0.001). This decreased with increasing age within the post-vaccine introduction population (76.1% for 1-5 years, 50.0% for 6-10 years, and 46.3% for 11-16 years). In addition, HBV chronic carriage was significantly (P = 0.003) reduced in the post- (1.4%) compared to the pre-vaccine introduction population (4.2%). The difference in prevalence of active HBV infection in the serologically exposed pre- and post-vaccine introduction populations was not statistically significant. Subset analyses showed that evidence of immunity was significantly (P < 0.001) higher in the HIV negative compared to the HIV positive subset in both populations. Universal hepatitis B vaccination has been a remarkable success, with a significant increase in immunity to HBV infection. The observation that HBV chronic carriage increases as immunity wanes over time calls into question whether the time has come to consider a pre-adolescence vaccine booster dose policy.

Hepatitis B virus infection in HIV-exposed infants in the Western Cape, South Africa

“…Only one mother in that cohort was HBeAg positive [32]. Another cross-sectional study from South Africa comparing pre-and post-vaccination cohorts over an almost 20 year period showed a decrease in HBsAg prevalence from 4.2% to 1.4% [33].…”

Hepatitis B virus infection in post-vaccination South Africa: Occult HBV infection and circulating surface gene variants

“…From a previous health facility-based hepatitis B serosurvey [2], 201 serum samples which tested positive for serological makers of exposure to HBV; HBsAg and/or antibody to HBV core antigen (anti-HBc), were identified out of a total sample size of 1206. These serologically exposed samples were the focus of this study.…”

“…Subsequent studies have reported a decline in the prevalence of chronic HBV infection since the vaccine’s introduction [2,35,36]. What threatens the benefits of vaccination is the emergence of HBV S gene variants due to immune selection pressure from the HBV vaccine [50].…”

Global Epidemiology of Hepatitis B Virus (HBV) Infection

“…In this setting, emerging data have outlined the beneficial impact of universal HBV vaccination. In South Africa, where HBV vaccination was introduced in 1995, immunity to HBV among subjects aged 1-25 years increased from 13 to 57 % in the post-vaccine era, resulting in a steady decline in HBsAg carriage from 4.2 to 1.4 % [55].…”