(366) Trends of COVID-19 Vaccine Adverse Event Following Immunization (AEFI): A One-year Retrospective Review Using the Passive Surveillance Data in the Nigerian National Database (Vigiflow).

Background: Since the introduction of the COVID-19 vaccines in Nigeria, NAFDAC has been working with multi stakeholder groups to ensure efficient utilization of the COVID-19 vaccines and mechanisms for their effective safety monitoring. The safety profile of the vaccines that have been rolled out were based on clinical studies conducted in foreign countries. As these COVID-19 vaccines are novel and with paucity of data to characterize their safety profile, it is imperative to review their safety data in Nigeria post authorization.

Objectives: To analyze the trends of AEFIs from Passive surveillance reports due to COVID-19 Vaccines in the Nigeria National Database ‘Vigiflow” from March 2021 to June 2022

Methods: A retrospective review of all reported AEFIs in the Vigiflow database using passively collected AEFI surveillance data from March 2021 to June 2022 was carried out. The key parameters of interest include demographics, number of AEFI reported for each type of COVID-19 vaccine and seriousness criteria. Descriptive and inferential statistical methods of analyses were employed. A multivariable logistic regression model was constructed to identify factors associated with any adverse effects (vs no adverse effects). Levels of significance were set at 0.05 with Confidence Interval (CI) at 95%.

Results: A total of 14,959 AEFIs were reported from March 2021 to June 2022. Amongst the AEFIs reported for various COVID-19 vaccines, fever, accounted for most AEFI with 31.8% (n = 7065). Headache and Injection site pain were other common AEFIs to COVID-19 vaccines with 13.2% (n = 2927) and 11.4% (2525) respectively. AstraZeneca brand of the vaccine had the highest number of AEFIs with 64.76% (n= 9687), followed by Moderna brand with 33.08% (n=4948), Pfizer brand, 1.37 (n= 205) and Janssen brand, 0.80%. Fifty-eight (58) AEFIs were identified as serious AEFIs and were investigated in detail by the State Immunization Programme Officers and reviewed by the National Expert Committee (NEC). Six of the top 10 AEFIs namely fever, headache, general body pain, pain at injection site, tiredness and local reaction were associated with vaccine brand type. Muscle aches and local reaction were associated with gender while local reactions and pain at the injection site were associated with vaccine doses. None of the AEFIs were associated with age group.

Conclusions: A sizeable number of AEFIs were reported in general but the frequency of serious AEFI was low. The overall AEFI reporting rate ranged from 0.019 to 0.40 per 1000 for the four COVID-19 vaccine products in Nigeria. All the four brands of COVID-19 granted emergency use listing approval were well tolerated and no safety concern was identified. Therefore, concluding that the safety benefit of COVID-19 vaccine outweighs the risks.