Vaccine safety: Assessing the prevalence and severity of adverse events following COVID-19 vaccination amongst healthcare workers in tertiary health facilities in Nigeria

Background: Vaccines, including COVID-19 vaccines, are known to be cost-effective interventions for disease prevention and control. However, adverse events following immunisation (AEFI) may challenge the acceptance of these vaccines. This study assessed the prevalence and severity of COVID-19-related AEFI amongst healthcare workers at tertiary health facilities in Nigeria. Materials and Methods: This descriptive, cross-sectional study was conducted among healthcare workers who had received the COVID-19 vaccine. A multi-stage sampling technique was used to select participants from six Tertiary Health Facilities in Nigeria. Ethical approval (NHREC/01/01/2007-19/07/2021) was obtained from NHREC. Data were analysed using IBM® SPSS version 25 and categorical variables were presented in tables/charts using frequencies and proportions. Results: A total of 2130 respondents participated in the study, with a mean age of 37.4 ± 9.1 years. Most of the respondents, 1674 (78.6%), had two doses of the vaccine, and the overall prevalence of AEFI was 813 (38.2%). Common among the AEFI reported following the administration of the first dose of the vaccine were fever 649 (30.5%) and pain at the injection site 644 (30.2%), while it was pain at the injection site 216 (10.1%) and fever 173 (8.1%) for second dose. The higher proportions of AEFI were mostly mild to moderate. Conclusion: The study observed a relatively low prevalence of AEFI, with the commonly reported ones being fever and injection site pain. It is crucial that countries continuously collect the data on AEFI and establish causality as a way to improve quality and guarantee vaccine safety.