Side effects of Sputnik V, Oxford–AstraZeneca, Sinopharm, and Covaxin and their associations with other variables among healthcare workers of a tertiary hospital in Iran

•83.1% of participants showed at least one side effect.•Oxford–AstraZeneca and Sputnik V had the most frequent side effects.•Injection site pain was the most common local side effect.•Body/muscle pain, fever, headache, and fatigue were the most common systemic side effects.•Among the first-dose recipients of the Sputnik V vaccine, the prevalence of SEs was higher in those aged ≤ 31 years than those aged > 31 years.. Misinformation about the prevalence of COVID-19 vaccines' side effects (SEs) has led to concerns about and mistrust of vaccine safety. Thus, this study aimed to evaluate the prevalence of COVID-19 vaccines' SEs. In a cross-sectional survey-based study on the healthcare workers (HCWs) of a tertiary hospital in Iran, the SEs of Sputnik V, Oxford–AstraZeneca, Sinopharm, and Covaxin were evaluated through a face-to-face interview by a researcher-made questionnaire. A total of 368 HCWs received at least one dose of a COVID-19 vaccine. The prevalence of people with at least one SE was higher among those who received the Oxford–AstraZeneca (95.8 %) and Sputnik V (92.1 %) vaccines than those who received Covaxin (70.5 %) or Sinopharm (66.7 %). Following the first and second doses, injection site pain (50.3 % and 58.2 %), body/muscle pain (53.5 % and 39.4 %), fever (54.5 % and 32.9 %), headache (41.3 % and 36.5 %), and fatigue (44.4 % and 32.4 %) were the most common SEs. Overall, SEs were often initiated within 12 h and subsided within 72 h of vaccination. The prevalence of SEs after the first dose of Sputnik V was higher among those aged ≤ 31 years (93.3 %) than those aged > 31 years (80.5 %). In the Sputnik V group, the number of SEs experienced after the first dose was higher in women with underlying diseases than those without such diseases. Furthermore, the body mass index of participants with SEs was lower than that of participants without SEs. Compared to Sinopharm or Covaxin, the Sputnik V and Oxford–AstraZeneca vaccines were associated with a higher prevalence of SEs, a greater number of SEs per individual, and more severe SEs.