Risk factors for delay in age-appropriate vaccinations among Gambian children

Background: Vaccination has been shown to reduce mortality and morbidity due to vaccine-preventable diseases. However, these diseases are still responsible for majority of childhood deaths worldwide especially in the developing countries. This may be due to low vaccine coverage or delay in receipt of age-appropriate vaccines. We studied the timeliness of routine vaccinations among children aged 12-59 months attending infant welfare clinics in semi-urban areas of The Gambia, a country with high vaccine coverage. Methods: A cross-sectional survey was conducted in four health centres in the Western Region of the Gambia. Vaccination dates were obtained from health cards and timeliness assessed based on the recommended age ranges for BCG (birth-8 weeks), Diphtheria-Pertussis-Tetanus (6 weeks-4 months; 10 weeks-5 months; 14 weeks-6 months) and measles vaccines (38 weeks-12 months). Risk factors for delay in age-appropriate vaccinations were determined using logistic regression. Analysis was limited to BCG, third dose of Diphtheria-Pertussis -Tetanus (DPT3) and measles vaccines. Results: Vaccination records of 1154 children were studied. Overall, 63.3 % (95 % CI 60.6-66.1 %) of the children had a delay in the recommended time to receiving at least one of the studied vaccines. The proportion of children with delayed vaccinations increased from BCG [5.8 % (95 % CI 4.5-7.0 %)] to DPT3 [60.4 % (95 % CI 57.9 %-63.0 %)] but was comparatively low for the measles vaccine [10.8 % (95 % CI 9.1 %-12.5 %)]. Mothers of affected children gave reasons for the delay, and their profile correlated with type of occupation, place of birth and mode of transportation to the health facilities. Conclusion: Despite high vaccination coverage reported in The Gambia, a significant proportion of the children’s vaccines were delayed for reasons related to health services as well as profile of mothers. These findings are likely to obtain in several countries and should be addressed by programme managers in order to improve and optimize the impact of the immunization coverage rates. This study was conducted from January to June 2011 at the infant welfare clinics (IWC) of Fajikunda, Serrekunda and Sukuta Health Centres and Jammeh Foundation for Peace Hospital in the Western Region of The Gambia. These facilities serve an area of about 1,705 square Km with a population of about 392,000 people of which the majority are farmers or civil servantsThe IWC services include immunization services, growth monitoring, general health and nutrition education. In The Gambia, every newborn is given a health card where EPI vaccinations and dates of administration of the vaccines are recorded by immunization officers. The health cards also contain information such as birth record, vaccination schedules and monthly weight measurements for growth monitoring. The mothers are allowed to take the health card home and present it at all clinic visits. This was a cross-sectional survey targeting children aged between 12 and 59 months attending the health centres with their health cards on the survey day. The survey team was made of two clinicians and four field assistants who had experience in epidemiological surveys and were familiar with immunization dynamics in the study areas. The field assistants gave sensitisation talks about the study to the mothers attending the immunization clinics with their children. After this, the field assistants identified potentially eligible mother-child pairs and further individualised consent discussions were held. Consequent upon granting a written informed consent, the clinicians and field assistants obtained the following information from the child’s health card: date of birth (DOB), birth order, sex, place of birth and dates of the administered vaccines. This was followed by administration of a purpose-designed, structured questionnaire to the mothers. The questionnaire covered information on mother’s age, residence, parent’s level of education, parent’s concerns and perception about the vaccine benefits. In addition, mothers of children with delayed vaccination schedules were probed to give reasons for the delays. As the sample size was not stratified by study sites and age-groups of the target population, consenting mothers were enrolled in each recruitment site irrespective of the child’s age while children without verifiable records were excluded from this study. Based on the proportion of children who had delayed vaccinations in Rietvlei, South Africa (42 %) [13], a precision of 3 % and a 95 % confidence interval, a sample size of 1040 children was required. After adjusting for attrition rate of 10 % the sample size was approximately 1144. A complete vaccination schedule was defined as having received a dose of BCG (birth – 8 weeks), three doses of DPT-Hib-HBV [DPT1/OPV1 (6 weeks – 14 weeks); DPT2/OPV2 (10 weeks – 18 weeks); DPT3/OPV3 (14 weeks – 24 weeks)] and a dose of measles vaccine (38 weeks – 52 weeks) respectively (Table 1). The age at vaccination was recorded in days (date of vaccination minus date of birth). Timeliness of vaccination of a particular antigen was assessed against the WHO recommended range as already indicated above. Timeliness was categorised as follows: (a) too early (vaccine was received earlier than the recommended age); (b) timely (vaccine was received within the recommended period above); (c) delayed if received after the window period. Data were double entered into a Microsoft Access database and analysed using Stata 12.0 (College Station, Texas 77845 USA). Categorical variables were presented using proportions and continuous variables described using an appropriate measure of dispersion: means (standard deviations) or medians (Inter Quartile Range). Logistic regression was used to analyze factors associated with delay in receipt of each vaccine and delay. We did not include maternal age in multivariate analysis because it was correlated with birth order of the child (r = 0.66, p < 0.001). The study was approved by the Gambian Government/Medical Research Council Joint Ethics Committee. A written informed consent was obtained from the respondent before the questionnaires were administered.