Incidence of Adverse Events Following Immunization (AEFIS) of Covid-19 Vaccines in Ghana

Abstract

Introduction: To fight the COVID-19 pandemic, vaccines form part of an important public health tool in this quest. In Ghana, five (5) COVID-19 vaccines (COVISHIEDTM (AstraZeneca), SPIKEVAXTM, COMIRNATYTM, Gam-COVID-Vac and Janssen) which were given Emergency Use Authorization (EUA) have been used in the mass vaccination campaign since March 2021. Since early phase trials of the vaccines were mostly not conducted in Africans, assessing safety data during their deployment under real-life conditions in the Ghanaian population is important. Methods: This study was a retrospective study involving secondary safety data analyses of AEFI reports from active (cohort study) and passive surveillance (spontaneous reporting) of the 5 COVID-19 vaccines deployed in the mass vaccination campaign involving adults in Ghana since March 2021. Data obtained from the primary data host institution (FDA) in Microsoft Excel spreadsheets and on paper forms, were cleaned and imported into STATA I/C 16 (Stata Corp LLC, Texas, USA) for analyses. Descriptive characteristics of study participants were done using frequency and percentages for categorical variables, and median and interquartile range for continuous variables. Bar- and pie charts were also used to describe characteristics such as chronic medical conditions, the cumulative incidence of adverse events following immunization (AEFIs), the various forms and number of AEFIs experienced, as well as the latency of AEFIs experienced. For the cohort event study, the cumulative incidence, the incidence rate per 100,000 person days, and the incidence rate ratios were estimated using the dose of vaccines as the unit of analysis. The Pearson chi-square test was used to assess the factors associated with the cumulative incidence of AEFIs among study participants. The Cox proportional hazard regression model was used to assess the factors associated with the risk of AEFIs among the study participants. For the analysis of the spontaneous (self-reporting) data, descriptive analysis was performed across the various vaccine types. The Pearson chi-square test was also used to assess the association between the severity of AEFIs experienced and the background characteristics. The binary logistic regression model was also used to assess the factors associated with severe AEFIs and deaths following the occurrence AEFIs among vaccine recipients. Similarly, the outcome of the AEFIs experienced was also described across the background characteristics and the Pearson chi-square test was used to assess the association. All statistical analyses were considered significant with p-values less than 0.05. Approval was obtained on 13th June 2022 from the FDA to use the AEFI data and ethics approval was obtained from the Ghana Health Service Ethics Committee on 18th October 2022. Results: The overall incidence of AEFIs among the 6,100 vaccine recipients in the cohort study was 14.0% (851/6,100). For the spontaneous reports, of the 10,733,719 vaccinated population, 8,498 AEFIs were reported giving an incidence of about 0.049% (49 per 100,000 persons). In the cohort study, most AEFIs (88.7%) occurred by the following day after vaccination and the proportion of females who experienced AEFIs (15.6%) was higher than that of males (12.4%) and this was statistically significant (p<0.001). Also, in both the cohort study and the spontaneous reports, the incidence of AEFIs was higher in the younger age groups compared with those in the 60 years and older age group with the most common AEFIs being headache, body pain, fever and injection site pain. These events were mostly mild and resolved within a few days. The occurrence of AEFIs was found to be dependent on the age, vaccine type, vaccine dose as well as the enrolment site of vaccine recipients in the cohort study. Also, in terms of severity of the AEFIs, age and vaccine type were factors found to be associated with having a severe adverse event in spontaneous reports. Conclusion: There was a low incidence of AEFIs following all 5 COVID-19 vaccines used in Ghana since the mass immunization with the events being generally mild and resolving within a few days. The public should be made aware that the vaccines are safe and encouraged to get vaccinated to increase vaccine coverage across the country.