Hepatitis B surface antigen seroprevalence among children in the Philippines, 2018

The World Health Organization Western Pacific Region (WPR) set a hepatitis B virus (HBV) control target to achieve HBV surface antigen (HBsAg) prevalence of <1% among children aged 5 years by 2017. The estimated HBsAg prevalence in the Philippines among adults was 16.7% during the pre-vaccine era. We estimated the HBsAg seroprevalence among children aged 5-7 years to measure the impact of vaccination. We conducted a household serosurvey, using a three-stage cluster survey methodology (provinces, clusters, and households). We estimated HBsAg prevalence using a rapid, point-of-care HBsAg test and calculated vaccination coverage by reviewing vaccination records or by caregiver recall. A questionnaire was administered to assess demographic variables for the child and family. We assessed the association between chronic HBV infection, vaccination coverage, and demographic variables, accounting for the complex survey design. Of the 2178 children tested, HBsAg was detected in 15 children [0.8%, 95% confidence interval (CI): 0.4, 1.7]. Only two of the HBsAg-positive children had been fully vaccinated against HBV. Based on documented vaccination or caregiver recall for the survey population, hepatitis B vaccine birth dose (HepB-BD) coverage was 53%, and the third dose hepatitis B vaccination (HepB3) coverage was 73 percent. Among the 1362 children with documented HepB-BD, timely HepB-BD coverage (given within 24 h of birth) was 43%; children born outside a health facility were less likely to receive a timely HepB-BD than those born in a health facility (adjusted odds ratio 0.10, 95% CI: 0.04, 0.23). HBsAg prevalence among children in the Philippines has decreased compared to the prevalence among adults in the pre-vaccination era. Strategies to further reduce HBsAg prevalence include ensuring that all children, whether born in health facilities or at home, receive a timely HepB-BD, and increasing HepB-BD and HepB3 coverage to reach the WPR goals of ≥95% coverage.