The evolution of post-vaccination adverse reactions and antibody responses in healthcare workers after receiving the inactivated SARS-CoV-2 vaccine at Pamukkale University Hospital

Vaccines play a crucial role in preventing infectious diseases and managing outbreaks by building herd immunity. However, there are still individuals who have vaccine hesitancy or concerns about vaccines. Often rooted in limited knowledge, misconceptions, or safety apprehensions, these concerns have prompted an increased focus on scientific investigations into vaccine side effects and safety. These studies have contributed to the accumulation of robust safety data throughout the vaccine development process, fostering a more comprehensive perception of vaccine-related adverse events. Vaccine side effects are generally mild and temporary, and they are part of the normal immune response observed in the majority of vaccine recipients. These effects may include mild fever, muscle pain, fatigue, or local reactions. Serious side effects are rare, and when compared to the potential risks of vaccination, they are considered insignificant. The aim of this study was to demonstrate the potential role of the side effects following the administration of the first and second doses of CoronaVac in achieving immunity, as well as to improve our understanding of vaccine-related side effects. Additionally, the study aimed to identify potential risk factors associated with these side effects and contribute for future vaccination strategies. The study enrolled 648 healthcare workers who received the initial dose of the inactivated SARS-CoV-2 (SINOVAC, CoronaVac) vaccine from January 14 to January 21, 2021, and the second dose from February 11 to February 18, 2021. Blood samples were collected from the participants 14 days after the second dose to measure the antibody response. The vaccine antibody response was measured using the Abbott SARS-CoV-2 IgG II Quant kit, and a value of Anti SARS CoV 2 IgG ≥ 50 AU/mL was considered as a positive result. Following the initial dose, 61.2% (n=572) of the participants experienced at least one side effect, while 38.8% (n=362) reported no side effects or adverse events. After the second dose, at least one side effect was observed in 63% (n=410) of the participants, with no adverse events reported in 36.7% (n=238). Notably, no life-threatening reactions including anaphylaxis were observed following the administration of both doses. After the first dose, pain at the injection site (44.4%) was the most common local side effect. The most frequently observed systemic side effects included headache (22.7%), fatigue (21.3%), muscle pain (7.2%), back pain (5.3%), and local swelling at the injection site (5.2%). Following the second dose, the most common side effects were pain at the injection site (28.2%), fatigue (14.5%), headache (13.4%), muscle pain (6.5%), and arthralgia (4%). The likelihood of experiencing side effects such as pain at the injection site headache , fatigue , myalgia, back pain, local swelling at the injection site, fever nausea-vomiting, redness at the injection site, itching at the injection site, cough after the first dose, and pain at the injection site, headache, fatigue, nausea-vomiting and myalgia after the second dose was found to be higher in females compared to males (p<0,001, p<0,001, p<0,001, p=0,012, p=0,004 p=0,003, p=0,025, p=0,034, p=0,034 p=0,01, p=0,047, p=0,03, p= 0,002, p= 0,008, p=0,033, p=0,007). Pain at the injection site (p<0.001) and fatigue (p=0.002) after the first dose and swelling at the injection site after the second dose were associated with younger age (p<0.001). The probability of experiencing hypertension after the first dose (p=0.006) and headache after the second dose (p=0.009) was associated with older age. Individuals with normal weight were found to have a higher probability of experiencing pain at the injection site after the first dose (p<0.001). A history of previous COVID-19 infection was associated with pain at the injection site after the first dose (p=0.021) and itching at the injection site after the second dose (p=0.003). The average antibody level of female participants, was significantly higher than that of male participants (p=0.032). Higher antibody levels were detected in the youngest age group (p=0.002). Having lung disease was associated with lower anti-SARS-CoV-2 spike IgG levels (p=0.036). Overall, this study supports that participants between the ages of 18-66 tolerated the vaccine well, and no serious side effects were observed. It was determined that the developing immunogenicity of the vaccine was not affected by the occurring side effects, and factors such as age, gender, body mass index, and underlying diseases influenced the reactogenicity and immunogenicity of the vaccines.