Hepatitis B vaccine effectiveness among vaccinated children in Africa: a systematic review and meta-analysis

Globally, 257 million people have chronic hepatitis. Even though a safe and effective prophylactic vaccine against HBV infection has been available, it causes significant morbidity and mortality. HBV vaccines were designed to improve or modulate the host immune responses. The effectiveness of the vaccine is determined by measuring serum hepatitis B surface antibody (Anti-HBs) level. Therefore, this systematic review aimed to evaluate the effectiveness of hepatitis B vaccine among vaccinated children.

Preferred reporting items for systematic review and meta-analysis (PRISMA) guidelines was applied for systematically searching of different databases. Only cross-section studies measuring the level of anti-HBs of vaccinated children were included. The seroprotective level with anti-HBs > 10mIU/ml was extracted. The meta-analysis was performed using statistical software for data sciences (STATA) version 14. Effectiveness estimates were reported as a proportion of anti-HBs level. The heterogeneity between studies was evaluated using the I² test, and I² > 50% and/or P < 0.10 was considered significant heterogeneity. Significant publication bias was considered when Egger's test P-value < 0.10. The new castle Ottawa scale was used to assess the quality of the studies.

A pooled sample size of the included papers for meta-analysis was 7430. The pooled prevalence of seroprotected children was 56.95%, with a heterogeneity index (I²) of 99.4% (P < 0.001). 35% of the participants were hypo-responders (10-99mIU/ml) and 21.46% were good responders (> 100mIU/ml). Based on subgroup analysis using country of studies conducted, the highest prevalence of anti-HBs was 87.00% (95% CI: 84.56, 89.44), in South Africa, and the lowest was 51.99% (95% CI: 20.41-83.58), with a heterogeneity index I² = 70.7% (p = 0.009) in Ethiopia.

Hepatitis B vaccine seroprotective level in the current pooled analysis have suboptimal, which failed to demonstrate consistent effectiveness for global hepatitis B virus elimination plan in 2030. Using consistent age group may have a significant value for the decision of the HB vaccine effectiveness. A significant heterogeneity was observed both in studies conducted in Ethiopia and Egypt. Therefore, the impact of HB vaccination on the prevention of hepatitis B virus infection should be assessed regularly in those countries. Future meta-analysis is needed to investigate all possible vaccines in a separate way of reviewing, which will lead to a strong conclusion and recommendations.