Potential Adverse Effects of COVID-19 Vaccines on Iranian Healthcare Workers: Comparison of Four Avai able Vaccines in Tehran: A Retrospective Cross-sectional Study

Objectives: This study aimed to compare four COVID-19 vaccines for their potential extensive side effects and the relationship between the side effects and age, body mass index (BMI), and history of COVID-19 infection. Methods: This cross-sectional study was conducted from June to August 2021 among 1474 healthcare workers of seven selected hospitals in Tehran, Iran. All the subjects were vaccinated (91.7% received two doses and 8.3% received one dose) with one of four vaccines, Sputnik, Covaxin, AstraZeneca, and Sinopharm, at least 10 days before the study. The incidence of 47 side effects was measured after vaccination. Results: Over half of the participants (59.4%; n = 876) were 20–29 years of age, with the mean and average BMI being 26.1±9.0 and 23.5±3.4, respectively; 36.0% (n = 530) were previously diagnosed with COVID-19. There was no significant relationship between age and the incidence of side effects for AstraZeneca, Sputnik, and Covaxin; however, the occurrence of side effects of Sinopharm was significantly higher (p < 0.001) among younger healthcare workers. There was no significant relationship between BMI and the incidence of side effects for all four vaccines. However, in the group with a history of COVID-19 disease, health care workers vaccinated with the Sinopharm vaccine showed significantly (p < 0.001) more complications. The occurrence rate of at least one adverse effect and referral to medical centers for AstraZeneca, Sputnik, Covaxin, and Sinopharm vaccines were 24.9–93.9%, 18.2–86.0%, 14.8–77.0%, and 3.5–37.2%, respectively. The highest and lowest rates were found for AstraZeneca and Sinopharm showing a significant (p < 0.001) difference. The most commonly observed side effects for the AstraZeneca vaccine included fever (64.4%), fatigue (62.5%), and muscle pain (59.9%); for Sputnik muscle pain (59.8%), fever (49.5%), and fatigue (49.5%); for Covaxin fever (49.2%), topical reaction (41.0), and fatigue (34.4%); and for Sinopharm fever (18.7%), topical reaction (17.9%), and fatigue (16.6%). Inactivated virus vaccines (Sinopharm and Covaxin) showed a lower (39.7%) occurrence rate of side effects compared to viral vector vaccines (AstraZeneca and Sputnik; 90.6%). The most likely time for the vaccines to exert side effects was the first 24 hours after vaccination. Conclusions: We found no significant relationship between age, BMI, history of COVID-19 disease, and the incidence of side effects in healthcare workers vaccinated with any of th