Adverse reactions to mRNA coronavirus disease 2019 (COVID-19) vaccine for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in 576 medical staff

Masamichi Hayashi; Hayashi M; Sayako Morikawa; Morikawa S; Goto Y; Yusuke Goto; Takazumi Yoshida; Yoshida T; Yutaro Kimura; Kimura Y; Kazuyoshi Imaizumi; Imaizumi K

doi:10.20407/fmj.2021-009

Adverse reactions to mRNA coronavirus disease 2019 (COVID-19) vaccine for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in 576 medical staff

Masamichi Hayashi, Hayashi M, Sayako Morikawa, Morikawa S, Goto Y, Yusuke Goto, Takazumi Yoshida, Yoshida T, Yutaro Kimura, Kimura Y, Kazuyoshi Imaizumi, Imaizumi K

Fujita medical journal · 2022 · vol. 8(3) , pp. 79–82 · doi:10.20407/fmj.2021-009 · PMID:35949514 · PMC9358674

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⚙ AI-generated summary by qwen3.7-flash, 2026-08-23 ⓘ

This study evaluated adverse reactions to Pfizer mRNA COVID-19 vaccines in 576 Japanese medical staff, finding that most side effects were mild and no serious anaphylaxis occurred.

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⚙ AI-generated deep summary by qwen3.7-flash, 2026-08-23 · read from full text ⓘ

This study investigated adverse reactions to the Pfizer-BioNTech mRNA vaccine in 576 medical staff members at a Japanese hospital, documenting symptoms following both the first and second doses. The results indicated that while adverse events were rare after the initial vaccination (1.0%), they increased significantly to 11.1% after the second dose, with fever being the most common symptom reported by 58 subjects. Although the paper lists endometriosis among the pre-existing medical histories of four participants, it does not analyze any specific interactions between the condition and the vaccine or discuss pathophysiological mechanisms related to gynecological disorders. Relevance to endometriosis: listed as one of several comorbidities present in the study population, though the paper's main focus is on general vaccine safety in healthcare workers.

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Abstract

OBJECTIVES: Various measures have been taken to curb the COVID-19 epidemic, but their effect has been limited. Vaccines are expected to make a definite improvement. In Japan, vaccination began in February 2021. However, there are very few reports of adverse reactions to mRNA vaccines for the new coronavirus (SARS-CoV-2) in Japanese people. Therefore, adverse reactions in 576 vaccinated medical staff at the author's hospital were investigated. METHODS: The subjects were 576 medical staff who wished to receive the new coronavirus (SARS-CoV-2) vaccine. The first vaccination was performed with Pfizer's new coronavirus mRNA vaccine (commercial name: Comirnaty intramuscular injection) from March 8 to March 15, 2021. The second vaccination was performed from March 29 to April 5, 2021, at an interval of more than 21 days from the first vaccination. RESULTS: Adverse reactions were seen in six subjects in the first vaccination. There was dyspnea in one subject, arthralgia in one subject, fever/malaise in three subjects, and left axillary pain and lymphadenopathy in one subject. One subject had a reaction at the vaccination site that needed to be addressed. At the second vaccination, adverse reactions were observed in 64 subjects. There was fever in 58 subjects, malaise in 21 subjects, arthralgia in 12 subjects, aching pain in 11 subjects, headache in six subjects, chills in six subjects, nausea in three subjects, redness in two subjects, dizziness in two subjects, hives in two subjects, swelling in two subjects, cough in one subject, and itching in one subject (some had multiple adverse reactions). Fever was observed in the range of body temperature from 37.4 to 38.9 degrees. CONCLUSIONS: Most of the adverse reactions to the COVID-19 vaccine were mild, and no serious anaphylaxis was observed. Vaccination was considered perfectly feasible if attention is paid to adverse reactions.

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Section 1

As regards COVID-19 vaccines, many adverse reactions were experienced at the second vaccination, but most of them were mild, and serious anaphylaxis was not observed. As reported from Europe and the United States, it was concluded that vaccination is perfectly feasible if attention is paid to adverse reactions. From now on, the latest adverse reaction information should always be reviewed, and vaccination performed appropriately in the light of that information.

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