Effect of introduction of pentavalent vaccine as replacement for Diphtheria-Tetanus-Pertussis and Hepatitis B vaccines on vaccination uptake in a health facility in Nigeria.

Background: The introduction of a new vaccine into an immunization programme may affect the immunization system negatively or positively. The aim of this study is to determine the effect of the introduction of the pentavalent vaccine as replacement for DTP and Hepatitis B vaccines on timeliness, completion of the schedule and dropout rates among children attending a health facility.

Methodology: This was a retrospective cohort study which involved extracting immunization records of children attending the Institute of Child Health Child Welfare Clinic between June 2011 and May 2013. Pentavalent vaccine was introduced as a replacement for DTP and Hepatitis B vaccines in June 2012. The uptake, timeliness and dropout rates of different vaccines in the immunization schedule were determined for children who commenced immunization in the pre, peri and post introduction phases.

Results: A total of 1110 children were studied - 190, 410 and 510 who commenced vaccination in the pre, peri and post introduction phases of the pentavalent vaccine respectively. Uptake was significantly higher for all vaccines in the post introduction phase compared to pre and peri introduction phases (p<0.001). Completion of the immunization schedule by 60.2% of the children who commenced vaccination in the post introduction phase was higher than the 31.6% and 41.7% for the pre and peri introduction phases respectively (p<0.001). Significantly more visits were required to complete the schedule in the peri introduction phase compared to the pre and post introduction phases p<0.001. Delay in receipt of the three doses of DTP/PENTA was significantly longer in the peri introduction phase compared to pre and post introduction phases.

Conclusion: The introduction of pentavalent vaccine significantly improved uptake of vaccines and completion of the schedule but resulted in prolonged delay in receipt of vaccines during the introduction period.