Korean J Fam Pract.  2021 Oct;11(5):357-364. 10.21215/kjfp.2021.11.5.357.

Comparison of Adverse Events of the First Dose and the Second Dose after Vaccination of the COVID-19 Pfizer Vaccine

• Kwon BK
• Park JM
• Kim WK

• KMID: 2521440
• DOI: http://doi.org/10.21215/kjfp.2021.11.5.357

Abstract

Background
Among the various COVID-19 vaccines developed to counter the pandemic caused by SARS-CoV-2 virus, BNT162b2 developed by Pfizer/ BioNTech was also introduced in Korea. But domestic studies on adverse events resulting from BNT162b2 are insufficient. Therefore, this study aims to help predict and prepare for adverse events in the future to ensure safe vaccination.
Methods
A total of 139 vaccine recipients were asked to report adverse events through self-report questionnaire for a period of 10 days after dose 1 and dose 2 of BNT162b2. Local and systemic adverse reactions were identified, and each adverse reaction was divided into four stages according to severity.
Results
The onset of adverse events was significantly slower (P<0.001) and the duration was longer (P<0.001) after dose 2. The frequency and severity of all local reactions, and the frequency and severity of nausea/vomiting (P=0.005), diarrhea (P=0.002), headache (P<0.001), fatigue (P<0.001), myalgia (P<0.001), fever (P<0.001), and other reactions (P=0.003) among systemic reactions, increased after dose 2.
Conclusion
The severity and frequency of the adverse events increased after dose 2 of BNT162b2, when compared with the period after dose 1.

Keyword

COVID-19 Vaccine; MRNA (Pfizer-Biontech); Vaccine Adverse Events; Korea