Comparison of adverse events following pentavalent and diphtheria-tetanus-pertussis vaccines among Nigerian children.

Introduction: Adverse events following immunization (AEFI) may follow the use of any vaccine. There is thus a need for documentation of the types and prevalence of AEFIs for each vaccine and early identification of new events or those occurring at rates higher than expected. When one vaccine replaces another, it is important to document the safety of the new vaccine as well as compare to that of the old. In this study, we aimed to document the AEFIs following the use of pentavalent vaccine recently introduced into the National Programme on Immunization and compare with those of diphtheria-tetanus-pertussis (DTwP) vaccine which it replaced.

Methods: This was a retrospective cohort study on infants with at least 2 immunization visits who commenced immunization between June 2011 and May 2013 at the Child Welfare Clinic of Institute of Child Health, University of Benin, Nigeria. At every visit for immunization, the caregiver is asked about any reaction that followed the previous immunization, and this is documented in immunization registers which data were reviewed for this study.

Results: There were 2475 doses of DTwP and pentavalent vaccines administered to 946 children. Adverse events following immunizations were reported following 487 (19.7%) doses. The prevalence of AEFIs following pentavalent vaccine (22.1%) was significantly higher than that following DTwP (13.5%) P < .0001. Significantly more AEFIs followed the first dose of either vaccine compared to subsequent doses P < .0001. The commonest AEFI reported for either vaccine was fever.

Conclusion: Adverse events following immunization following pentavalent vaccine although higher than that following DTwP was within expected levels.