Adverse events following immunization reporting and impact on immunization services in informal settlements in Nairobi, Kenya: a prospective mixed-methods study

Introduction: adverse events following immunization (AEFIs) are thought to contribute to cases of vaccine hesitancy, yet little data exists describing the state of reporting and management of AEFIs. This study investigated the occurrence and influence of AEFIs on vaccine hesitancy in an informal settlement of Nairobi. Methods: this was a prospective mixed-methods study involving 7 focus group discussions, 8 key informant interviews and 457 face-to-face interviews with caregivers. Caregivers were recruited at/or before the 6 week clinic visit and assessed for occurrence of AEFIs in their children at the subsequent 10- and 14-week visits and a follow-up two weeks following the 14 weeks visit via phone calls. Results: in this study, 12.3% (56/457) of the infants experienced an AEFI. Of these, 19 did not report for the next scheduled vaccine. Fever was the most common AEFI, for which most caregivers (66.7%) used Paracetamol as antipyretic, while 20.8% sought help from a nearby health facility. Three of the 56 AEFIs (convulsions) that occurred in study participants could be classified as severe reactions. Diphtheria, pertussis and tetanus (DPT 3) completion rate was 75.3%. Most (96.4%) caregivers considered immunization an important strategy for child survival. Vaccine hesitancy occurred among 3.6% of participants, 30% of whom attributed their hesitancy to occurrence of AEFIs. The review of health records revealed that no AEFI had been reported from any of the study facilities. Conclusion: cases of adverse events following immunization are not reported in Mathare Valley and they do have implications for vaccine hesitancy by some caregivers.