The Adverse Reactions of Pfizer BioNTech COVID-19 Vaccine Booster Dose are Mild and Similar to the Second Dose Responses: A Retrospective Cross-Sectional Study

BACKGROUND: Like other vaccines, Pfizer BioNTech’s COVID-19 vaccine efficacy against SARS-CoV-2 virus infections begins to decline within a few months after the 2(nd) dose. On August 12, 2021, the FDA allowed additional Pfizer BioNTch’s COVID-19 vaccine dose (3(rd) or booster dose) for individuals with weakened immunity. This study aimed to evaluate the short-term adverse reactions (ADRs) of the 2(nd) and the 3(rd) doses of the Pfizer BioNTech COVID-19 vaccine. METHODS: Information for this study was collected by Google Form questionnaire (online survey). The results included responses from 442 people, the majority from Saudi Arabia. RESULTS: The most common local ADRs following the 3(rd) dose were injection site pain, injection site hypersensitivity, and axillary lymph node swelling. The most common systemic ADRs were fatigue, muscle pain, bone pain, headache, and fever less than 38ºC. Less common systemic ADRs were shivering, fever more than 38ºC, nasal congestion and rhinorrhea, arrhythmia, cough, abdominal pain, chest tightness, nausea, diarrhea, vomiting, and tachypnea. Rare systemic ADRs were constipation, dizziness and vertigo, lack of concentration, sore throat, excessive hair loss, dysmenorrhea and heavy menstruation, and Bell’s palsy. Severe allergic reactions were reported by 2.6% of participants after the 2(nd) dose, compared with none after the 3(rd) dose. Nasal congestion and runny nose are more frequent after the 3(rd) dose. The ADRs of the 2(nd) and 3(rd) doses were significantly more prevalent in females. 12% of participants reported ADRs lasting more than one week after the 3(rd) dose compared to 5% after the 2(nd) dose. People ≤ 60 years were more affected by the vaccine ADRs. CONCLUSION: Most of the ADRs reported after the 3(rd) vaccine dose were consistent with the Pfizer vaccine information sheet and similar to the 2(nd) dose ADRs.