Assessing the burden of hepatitis B in South Africa, predicting disease prevalence and modelling the impact of hepatitis B birth dose vaccination

Abstract

In 2016, WHO adopted a resolution to eliminate hepatitis B by 2030, targeted at reducing disease burden. In South Africa, HBV disease burden has largely been estimated from community-based or sentinel studies, thereby limiting its accuracy. Since 2009, the WHO recommended the addition of a birth dose of the HBV vaccine to current vaccine schedules to mitigate the risks of vertical transmission. This intervention is crucial to reduce disease burden, given the increased risks of developing chronic disease if contracted at birth or infancy. Despite the introduction of the HBV vaccine into their EPI schedule in 1995, South Africa is yet to fulfil this recommendation. In this study, our objective was to assess HBV disease burden in the public health sector of South Africa through meticulous analyses of an extensive national dataset spanning 2015 to 2019. Additionally, we aimed to model the potential impact of a birth dose of the HBV vaccine using country-specific HBV prevalence data obtained from our own testing conducted on women attending antenatal care in 2017. Over the five years, the national HBV prevalence was 9.02%, declining gradually each year. Overall, males had consistently higher prevalence rates than females. The observed lower infection and higher immunity rates among vaccine-eligible individuals clearly demonstrated the positive impact of the HBV vaccine. Nevertheless, HBV infection among these individuals was quite concerning, highlighting the roll-over effects of suboptimal vaccine coverage rates. The prevalence of HBsAg among pregnant women was alarmingly high at 11.24%, further compounded by the high HBeAg prevalence among these women. These findings alerted us to the increased probability of vertical transmission, representing a concerning source of disease burden in the country. Among vaccine-eligible women under 19 years old, HBsAg prevalence was surprisingly high at 8.08%, noting that these women still had approximately 30 more years of potential child-bearing. These findings pose a serious threat to achieving, or even nearing, WHO elimination goals. Using a deterministic HBV transmission model to simulate the impact of a birth dose of the HBV vaccine, we estimated more than a three-fold reduction in chronic HBV infections and HBV-related deaths, specifically when considering new cases from initiation of our model. In essence, this represents a greater than three-fold reduction in HBV disease burden. Our findings are unique for South Africa given their national representation and country-specific model inputs. Despite the introduction of the HBV vaccine in 1995, hepatitis B remained highly endemic in South Africa. Adding a birth dose to the current HBV vaccination schedule and achieving optimal vaccine coverage rates will markedly reduce country HBV burden. We therefore recommend prompt implementation of a birth dose of the HBV vaccine, together with increased efforts aimed at improving HBV vaccine coverage rates to optimal levels.