Characterizing Zero-dose and Under-vaccinated Children among Refugees and Internally Displaced Persons in the Democratic Republic of Congo

"...results can be used to help decision-makers better prepare and implement effective interventions to improve vaccine coverage, and completion of vaccination schedules among refugees and IDPs [internally displaced persons] in the DRC [Democratic Republic of Congo] and achieve the goal of leaving no one behind."

The Democratic Republic of Congo (DRC) has one of the highest numbers of un and under-vaccinated children as well as number of refugees and internally displaced persons (IDPs) in the world. This study aims to determine and compare the proportion and characteristics of zero-dose (ZD) and under-vaccinated (UV) children among refugees and IDPs in the DRC, as well as the reasons for non-completeness of vaccination schedules. The goal is to guide the strategic implementation of the Expanded Program of Immunization (EPI) and to improve vaccine equity among vulnerable communities

Data were sourced from a rolling vaccination coverage survey conducted from September 10 2022 to July 3 2023, among refugees and IDPs in 12 provinces of the DRC. Information was collected by trained teams composed of composed of doctors and nurses, using a questionnaire configured in Kobo Collect. ZD was defined as a child aged 12-23 months who had not received any dose of pentavalent vaccine DTP-Hib-Hep B (by card or recall) and UV as a child who had not received the third dose of pentavalent vaccine. The proportions of non and under-vaccination and the associated factors using a logistic regression model are presented for ZD and UV children. The reasons for non-vaccination of these children are described using the World Health Organization (WHO)-Immunization behavioural and social drivers (BeSD) conceptual framework and compared using Pearson's Chi2 test.

The BeSD framework separates determinants of vaccination into four categories:
 

• Category 1 relates to people's thinking and feelings - e.g., fear of side effects.
• Category 2 relates to the social processes and "family norms" - e.g., family problems that reduce the importance of child vaccination.
• Category 3 focuses on the motivation factors or willingness to be vaccinated.
• Category 4 relates to programmatic and practical factors. Category 4 is further stratified into three groups: (i) geographical barriers (e.g., vaccination site being too far away), (ii) interpersonal/relational factors (e.g., poor reception of families by health workers), and (iii) organisational barriers (e.g., vaccination site not known by families, long waiting time, vaccination schedule not respected, and vaccines frequently out of stock).

Of 692 children aged 12 to 23 months included in the analysis, 9.3% (95% confidence interval (CI): 7.2-11.7%) were ZD, and 40.9% (95% CI: 95%: 37.2-44.6%) were UV. The Penta1/Penta3 drop-out rate was 34.9%. The proportion of ZD children among refugees and IDPs is lower compared to that of the general population, which is 19.1% (according to the results of a 2021 vaccination coverage survey). On the other hand, the proportion of UV children among refugees and IDPs is much higher than that of the general population, which is 25.5% (according to the results of the same survey). This situation suggests that more needs to be done to ensure completion of vaccination schedules, as these special populations seem to accept vaccination - illustrated by a large majority starting the vaccination schedule without completing it.

Children born at home or on the road had 7 times higher odds of being ZD than those born in a health facility (adjusted odds radio (AOR) = 7.45 (95% CI: 3.88-14.32)). This finding can be explained, in part, by the fact that women giving birth in a facility would be exposed during pregnancy to advice on the importance of vaccinating children - and doing so in a timely manner. UV children were significantly associated with mothers/caregivers being under 40, uneducated, farmers, ranchers, employed, rural residents, as well as with home or road births.

In terms of the BeSD framework:
 

• Reasons linked to people's perceptions and feelings, which may contribute to reducing parents' motivation to have their children vaccinated, were cited much more often for ZD (50.0%) than for UV (38.3%) children.
• Reasons related to social processes were cited for 2 in 5 of ZD children (40.6%), higher than for UV children (35.7%).
• Almost all respondent cited having "practical issues", with these reasons being cited by 90.5% of ZD children and by 97.1% of those who were UV. As for the results by sub-categories, the most cited reasons were those relating to the organisation of health facilities (in 88.1% of ZD and 93.7% of UV children). Next in line were reasons related to the interpersonal/relational factors of health workers: in 20.0% of ZD and 16.7% of UV children. Finally, "vaccination site too far" in 5% of ZD children and in 25% of UV children (25.0%).

In conclusion, ZD and UV children represent significant proportions in refugee and IDPs sites in the DRC. "This study also revealed that the reasons for ZD children were more often linked to challenges in motivating parents or caregivers to vaccinate, while for UV children, the reasons for not completing their vaccination schedule were more often linked to programmatic and practical problems in the health system."

Full list of authors, with institutional affiliations: Marcellin Mengouo Nimpa, World Health Organization (WHO) Country Office, Kinshasa, Democratic Republic of Congo (DRC); Aimé Cikomola Mwana-Wabene, Expanded Program of Immunization, Kinshasa, DRC; John Otomba, WHO Country Office, Kinshasa, DRC; Jean-Crispin Mukendi, Expanded Program of Immunization, Kinshasa, DRC; M. Carolina Danovaro-Holliday, WHO, Geneva, Switzerland; Franck-Fortune Mboussou, WHO African Regional Office, Brazzaville, Republic of the Congo; Dieudonné Mwamba, National Institute of Public Health, Kinshasa, DRC; Leandre Kambala, WHO Country Office, Kinshasa, DRC; Dolla Ngwanga, WHO Country Office, Kinshasa, DRC; Cedric Mwanga, WHO Country Office, Kinshasa, DRC; Sume Gerald Etapelong, WHO Regional Office for the Eastern Mediterranean (EMRO), Cairo, Egypt; Issaka Compaoré, Associés en Management public et Développement (AMD) International; Moise Désiré Yapi, WHO Country Office, Kinshasa, DRC; Daniel Katuashi Ishoso, WHO Country Office, Kinshasa, DRC, and University of Kinshasa