Vaccination Coverage and Risk Factors Associated With Incomplete Vaccination Among Children in Cambodia, Madagascar, and Senegal

Abstract

Background: Vaccination reduces mortality from infectious disease, which is the leading cause of death in children under 5 and bears a particularly high burden in low- and middle-income countries. The Global Vaccine Action Plan (2011-2020) has set a target of 90% vaccine coverage for all vaccines included in national immunization programs by 2020. The objectives of this study were to estimate vaccine coverage among children in Madagascar, Cambodia, and Senegal and to identify the risk factors associated with incomplete vaccination.

Methods: Using data from a community-based prospective cohort that included all newborn of some areas from 2012 to 2018 in these 3 countries, vaccine coverage was estimated for BCG, hepatitis B, oral polio, pentavalent (targeting diphtheria, tetanus, pertussis, hepatitis B, and Haemophilus influenzae type b), and measles vaccines. Risk factor analysis was performed with logistic regression models to identify correlates of incomplete vaccination.

Results: A total of 3606 children were followed up, and vaccine coverage was below the 90% threshold for most vaccines in all countries. Coverage was higher for vaccines recommended at birth and at 6 weeks, while a decrease in coverage for subsequent doses was observed for vaccines requiring several doses (23-47 points). Low birth weight (<2500 g) was an important risk factor for nonvaccination for vaccines recommended at birth in all 3 countries (adjusted odds ratio [95% confidence interval] ranging from 1.93 [1.11-3.38] to 4.28 [1.85-9.37]).

Conclusions: Vaccine coverage for common childhood vaccines was lower than World Health Organization recommendations, and multidisciplinary approaches may help to improve vaccine coverage and timeliness.

Keywords: Cambodia; Madagascar; Senegal; risk factors; vaccine coverage.

Figure 1.

Study design of the Bacterial Infections and Antibiotic-Resistant Diseases Among Young Children in Low-Income Countries (BIRDY) cohort and national immunization programs in Cambodia, Madagascar, and Senegal. A, Schedule of home visits of the BIRDY cohort by country and site. B, Vaccines recommended in the national immunization programs of Cambodia, Madagascar, and Senegal and included in the analysis. (Other vaccines are recommended in these countries, but not covered in this study.) A dose of hepatitis B vaccine is recommended at birth, within the first 24 hours, in Cambodia and Senegal but not in Madagascar. One dose of oral polio vaccine is recommended at birth, within the first 14 days, in Senegal and Madagascar only. A second dose of measles vaccine is recommended at 15 months in Senegal and 18 months in Cambodia, whereas in Madagascar, only 1 dose is recommended. Abbreviations: HepB, hepatitis B vaccine; OPV zero, oral polio vaccine at birth; OPV 1, oral polio vaccine recommended at 6 weeks; OPV 2, oral polio vaccine recommended at 10 weeks; OPV 3, oral polio vaccine recommended at 14 weeks; Penta, pentavalent vaccine (diphtheria, tetanus, pertussis, Haemophilus influenzae type b, hepatitis B).

Figure 2.

Vaccination coverage among children in Cambodia, Madagascar, and Senegal, 2012–2018. A, Vaccination coverage of BCG, oral polio, and hepatitis B vaccines at birth among children in Cambodia, Madagascar, and Senegal, 2012–2018. B, Vaccination coverage of catch-up BCG, pentavalent (diphtheria, tetanus, pertussis, Haemophilus influenzae type b, hepatitis B) (3 or 2 doses), oral polio (3 or 2 doses), and measles vaccines among children in Cambodia, Madagascar, and Senegal, 2012–2018. C, Vaccination coverage of different recommended doses of pentavalent, oral polio, and measles vaccines in Cambodia, Madagascar, and Senegal, 2012–2018. Abbreviations: BCG 14 days, BCG vaccine within the first 14 days; BCG catch-up, BCG vaccine within the first year; HepB 24 hours, hepatitis B vaccine within 24 hours after birth; Measles m9, measles vaccine recommended at 9 months; OPV 14 days, oral polio vaccine within the first 14 days from birth; OPV w6, oral polio vaccine recommended at 6 weeks; OPV 2 doses, oral polio vaccine 2 doses recommended at 6 and 10 weeks; OPV 3 doses, oral polio vaccine 3 doses recommended at 6, 10, and 14 weeks; Pentavalent, pentavalent vaccine (diphtheria, tetanus, pertussis, Haemophilus influenzae type b, hepatitis B); Penta 2 doses, pentavalent vaccine 2 doses recommended at 6 and 10 weeks; Penta 3 doses, pentavalent vaccine 3 doses recommended at 6, 10, and 14 weeks; Pentavalent w6, pentavalent vaccine recommended at 6 weeks; WHO, World Health Organization.