DETERMINANTS OF UPTAKE OF THIRD DOSES OF ORAL POLIO AND DIPHTHERIA-PERTUSSIS-TETANUS VACCINES IN IBADAN NORTH LOCAL GOVERNMENT AREA, NIGERIA

Abstract

High drop-out rates between the first and third doses of Oral Polio Vaccine (OPV) and Diphtheria Pertussis- Tetanus (DPT) vaccine have been reported, despite efforts to improve immunisation coverage. Although studies have explored factors associated with completion of either vaccine, there is paucity of studies on factors associated with completion of both vaccines. This study identified determinants of uptake of third doses of OPV(3) and DPT(3) among infants who received first doses of either/both vaccines at immunisation centres located in Ibadan North Local Government Area (IBNLGA), Nigeria. Using a cohort study design, 400 mother-child pairs were consecutively recruited at uptake of first doses of either DPT(1) or OPV(1) from the five primary, three secondary and two tertiary health facilities offering routine immunisation in IBNLGA. A semi-structured interviewer-administered questionnaire, which included socio-demographic variables, perception towards immunisation and a ten-point scale on mothers' knowledge of immunisation schedule, was used to collect data. Knowledge score was classified as satisfactory (≥5) and unsatisfactory (<5). Each child was followed up for 90 days (at 30-day intervals), to record dates of second and third doses of the vaccines from immunisation registers. Differences (missed opportunities) between uptake of the vaccines were also recorded. Descriptive statistics, log rank test and Cox regression were used to analyse data at p < 0.05. Mean age of mothers was 30.0±5.7 years and 58.8±24.4 days for children. Thirty six-percent of the children were first births, 92.5% of the mothers were married, and 91.8% had satisfactory immunisation knowledge. Some (28.0%) participants attended tertiary, 43.5% secondary and 28.5% primary health facilities. All the children received OPV 1, while 359 (89.8%) received first dose of DPT. Of these, only 74.3% and 43.5% received second and third doses of OPV, while 65.5% and 24.8% of those who took DPT 1 received the second and third doses respectively. Cases of missed opportunities were recorded during the first (9.3%), second (17.6%) and third (49.7%) visits. Median time to receiving OPV3 was 62.0 (95% Cl= 60.3-63.7) days and 63.0 (95% Cl= 59.1-66.0) days for DPT3. The time of uptake of OPV3 was significantly shorter anmong children who were first births (57.0, 95% CI= 54.9-59.0 days) than higher birth orders (61.0, 95% CI = 59.3-62.7 days). Children of married mothers had a significantly shorter time (63.0, 95% CI = 57.8-68.2 days) to receiving DPT3 than those whose mothers were unmarried (81.0, 95% CI = 76.4-85.6 days). Factors predictive of uptake of OPV3 were; first birth (HR = 1.66, 95% CI = 1.11-2.48) and attending a tertiary health facility (HR = 2.27, 95% Cl= 1.41-3.65), while attending a secondary health facility was significant for uptake of DPT-3 (HR = 2.43, 95% CI= 1.30-4.61). Determinants of uptake of third doses of the vaccines were type of health facility attended and child's birth order, while missed opportunity for immunisation was common. Hence, efforts to improve vaccination coverage should take into consideration sustaining awareness on the importance of completing immunisation schedule for children of higher birth orders and prevention of missed opportunity in health facilities.