Immunization Coverage and Associated Factors Among Children Aged 18 to 72 Months in Communities With High Malaria Transmission, Bioko Island

Objective: To estimate routine immunization coverage, compare coverage estimates derived from vaccination cards and caregiver recall, and investigate factors associated with incomplete immunization among children aged 18 months to 6 years in communities with a high malaria prevalence in the Malabo district of Equatorial Guinea. Methods: A cross-sectional survey was nested within a larger study and was conducted between September 2019 and March 2020. Children aged 18 months to 6 years living in 13 malaria-endemic communities in Malabo District, Bioko Island were enrolled. Immunization status was ascertained from vaccination cards or caregiver recall. Results: Of the 297 children, with verified immunization status, 86 (29%) were fully immunized according to the national schedule. Coverage estimates were similar whether verified by vaccination card (28%, 34/121) or caregiver recall (30%, 52/176). Children aged 18 months and 2 years had higher completion rates than children aged 2-6 years: 45% (39/86) versus 22% (47/211), aOR = 0.42, 95% CI [0.20, 0.87]). The other factors examined (sex, ethnicity andcommunity area) were not significantly associated with immunization status. Conclusion: Overall immunization coverage in this population was low. Younger children had higher completion rates, possibly reflecting improved program performance in recent years or differential recall bias. Further community based studies, in both urban and peri-urban areas needed to identify reasons for gaps in vaccination coverage and to inform targeted interventions.