The Common Systemic and Local Adverse Effects of the Sinovac COVID-19 Vaccine: An Observational Study From Pakistan.

Background Vaccination acts by boosting the capacity of a person's immune system to identify and effectively resist infection-causing bacteria and viruses, as it stimulates the immune system to respond to the vaccine's antigens. The immunological response may include local and systemic symptoms, including pain at the injection site and fever, respectively. The Sinovac vaccine is an inactivated virus vaccine made in China and is one of the most widely used vaccines in many countries; however, the side effects of the Sinovac vaccine have not been well-studied in our population. Therefore, this study assessed the prevalence of side effects experienced by participants after receiving the Sinovac vaccine. Methodology This multicenter, cross-sectional study was conducted using a non-probability sampling method. The duration of the study was six months from May 1, 2022, to October 31, 2022. A total of 800 participants who were completely vaccinated with the Sinovac vaccine were included in the study. For categorical data, frequencies and percentages were documented, while for continuous data, such as age, height, weight, and the duration of comorbidities, means and standard deviations were evaluated. Results The study findings showed that out of 800 participants, 534 (66.8%) were males and 266 (33.3%) were females, with a mean age of 41.20 ± 13.70 years. Among them, 162 (20.3%) had hypertension, and 104 (13.0%) had diabetes. Following the first dose of the Sinovac vaccine, fever was the most commonly reported side effect in 350 (43.8%) participants. Additionally, pain at the injection site in 238 (29.8%) participants, followed by swelling at the injection site in 228 (28.5%) recipients, were among other common side effects. Following the second dose of the Sinovac vaccine, fever was the most commonly reported side effect in 262 (32.8%) participants. Conclusions This study concluded that fever was the most frequent systemic side effect, whereas pain and swelling at the injection site were the most frequent local side effects following the administration of the first and second doses of the Sinovac vaccine. Both dosages of Sinovac were well-tolerated, and the majority of the adverse effects were minor and self-limiting.