Coverage and timing of children's vaccination: an evaluation of the expanded programme on immunisation in The Gambia

Abstract

Objective: To evaluate the coverage and timeliness of the Expanded Programme on Immunisation (EPI) in The Gambia.

Methods: Vaccination data were obtained between January 2005 and December 2012 from the Farafenni Health and Demographic Surveillance System (FHDSS), the Basse Health and Demographic Surveillance System (BHDSS), the Kiang West Demographic surveillance system (KWDSS), a cluster survey in the more urban Western Health Region (WR) and a cross sectional study in four clinics in the semi-urban Greater Banjul area of WR. Kaplan-Meier survival function was used to estimate the proportion vaccinated by age and to assess timeliness to vaccination.

Findings: BCG vaccine uptake was over 95% in all regions. Coverage of DPT1 ranged from 93.2% in BHDSS to 99.8% in the WR. Coverage decreased with increasing number of DPT doses; DPT3 coverage ranged from 81.7% in BHDSS to 99.0% in WR. Measles vaccination coverage ranged from 83.3% in BHDSS to 97.0% in WR. DPT4 booster coverage was low and ranged from 43.9% in the WR to 82.8% in KWDSS. Across all regions, delaying on previous vaccinations increased the likelihood of being delayed for the subsequent vaccination.

Conclusions: The Gambia health system achieves high vaccine coverage in the first year of life. However, there continues to be a delay to vaccination which may impact on the introduction of new vaccines. Examples of effectively functioning EPI programmes such as The Gambia one may well be important models for other low income countries struggling to achieve high routine vaccination coverage.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1. Map of The Gambia.

WCR: Western Coastal Region; LRR: Lower River Region; CRR: Central River Region; URR: Upper River Region. Dashed circles represent the demographic surveillance sites: Farafenni Health and Demographic Surveillance System (FHDSS), Basse Health and Demographic Surveillance System (BHDSS), and Kiang West Demographic surveillance system (KWDSS).

Figure 2. Frequency distribution of number of vaccinations received by age at vaccination (in weeks) for each of the study sites: a) North Bank region (2005–2012), b) South bank of the Upper River Region (2005–2012), c) West Kiang, Lower River Region (2005–2012), d) Western Health Region (June 2010), e) Greater Banjul Health facilities (2010–2011).

Blue line: Proportion vaccinated with BCG vaccine. Brown line: Proportion vaccinated with 1 dose of DPT vaccine. Green line: Proportion vaccinated with 2 doses of DPT vaccine. Orange line: Proportion vaccinated with 3 doses of DPT vaccine. Blue/Green line: Proportion vaccinated with measles vaccine. Red line: Proportion vaccinated with DPT booster.

Figure 3. Proportion of eligible children vaccinated and median age (in months) by vaccine type and by region in The Gambia.

Blue bars: proportion who received BCG on time. Brown bars: proportion who received DPT1 on time. Green bars: proportion who received DPT2 on time. Orange bars: proportion who received DPT2 on time. Turquoise bars: proportion who received measles vaccine on time. Red bars: proportion who received DPT booster on time. Blue line: Median age (in months) for BCG. Brown line: Median age (in months) for DPT1. Green line: Median age (in months) for DPT2. Orange line: Median age (in months) for DPT3. Turquoise line: Median age (in months) for measles vaccine. Red line: Median age (in months) for DPT booster. Vertical bars: Interquartilte range in months of age at vaccination.

Figure 4. Estimated proportion vaccinated on time by age (months) by vaccine for each geographical region in the Gambia for a) schedule 1 and b) schedule 2.

Blue bars: proportion who received BCG on time. Brown bars: proportion who received DPT1 on time. Green bars: proportion who received DPT2 on time. Orange bars: proportion who received DPT3 on time. Turquoise bars: proportion who received measles vaccine on time. Red bars: proportion who received DPT booster on time. Vertical bars: 95% confidence intervals.

Figure 5. DPT3 coverage, GNI and under-5 mortality rate by countries in the AFRO region.

Circle size represents size of under-5 mortality rate. (http://data.worldbank.org/indicator/SH.DYN.MORT). Blue circle: WHO estimates for The Gambia. (http://apps.who.int/immunization_monitoring/globalsummary). Green circle: URR and NBR combined. Grey circle: Western health region. Yellow circle: West Kiang, LRR. GNI: Gross National Income per capita.