Cohort Event Monitoring of COVID-19 Vaccine Reactogenicity in the Netherlands Using Patient Reported Outcomes

Background/Introduction: The rapid deployment of COVID-19 vaccines has put the safety of these vaccines in the spot light. So far four COVID-19 vaccines are approved in Europe: mRNA vaccines from Pfizer and Moderna and viral vector vaccines from AstraZeneca and Janssen. Common Adverse Events following Immunization (AEFI) for these vaccines include manifestation of the inflammatory response such as pain, redness, swelling and pyrexia. To provide more insight in differences in vaccinated population in terms of age, gender, and medical background in relation to reactogenicity, data from the Dutch COVID-19 vaccine Cohort Event Monitoring were used. Objective/Aim: To explore factors that are associated with the occurrence of COVID-19 vaccine reactogenicity after the first dose in the Netherlands. Methods: A web-based prospective cohort design using patient reported outcomes was used [1]. Dutch participant, vaccinated with a COVID-19 vaccine, and registered for this study during February to May 2021 were included. A baseline questionnaire gives information on participant characteristics (age, gender, length, weight), comorbidities, concomitant medication, use of an antipyretic drug several hours before or after vaccination, and a history of experienced COVID-19 disease demonstrated by a positive test. The questionnaire about AEFI was sent 7 days after vaccination. Multivariable logistic regression analysis was used for analysis, with significance level of < 0.05. Results: Out of 21.822 participants included, 11.542 (52.9%) experienced reactogenicity. Compared to the Pfizer vaccine, the highest odds ratio (OR) for developing reactogenicity was for the AstraZeneca vaccine (OR 4.18) followed by Moderna (OR 1.77), and Janssen (OR 1.74). Participants with a history of COVID-19 disease had a 2.3 increased odds for reactogenicity. Women had a 2.04 increased odds compared to men. Older participants experienced less reactogenicity. Compared to the age group < 50, the ORs for the age groups 50-60, 61-79, and > 80 were 0.51, 0.26, and 0.16 respectively. Comorbidities that were associated with reactogenicity were cardiac disorders (OR 1.15), musculoskeletal disorders (OR 1.34), respiratory disorders (OR 1.20), and infections (1.88). A body mass index of 25.0-29.9 and over 30 was negatively associated with reactogenicity (OR 0.90 and OR 0.71 respectively). Conclusion: This extensive study with over 21.000 participants demonstrated that, taken into account all factors in the