現在、新型コロナウイルス感染症(COVID-19)は世界的に流行し、深刻な公衆衛生上の問題となっている。慶應義塾は教育・研究機関であり、かつ医療機関を有しており、教育、研究、医療を維持していくために、COVID-19感染対策は重要である。特に、医療機関ではCOVID-19集団感染の発生リスクが高く、医療従事者のCOVID-19感染対策は重要である。医療従事者の適切なCOVID-19感染対策を検討するため、医療従事者である本学医学部・大学病院に所属する教職員・学生 約4000人を対象に新型コロナウイルス(SARS-CoV-2)の感染状況を調査した。2020年10月から2021年10月までに、SARS-CoV-2に感染した者の臨床情報を調査し、感染者数の推移と感染者の臨床的特徴を解析した。感染者数は74人であった。東京都の20代から50代の感染者数の多い月が1月（28,116人）、5月（16,115人）、8月（98,364人）であったが、医療従事者の感染者数はそれぞれ13人、1人、22人であった。3月に希望者を対象としたCOVID-19ワクチン接種が実施された。4月以降の感染者数は37人で、ワクチン接種後が25人、ワクチン未接種が12人であった。ワクチン接種後の発熱ありの感染者数は9人、ワクチン未接種の発熱ありの感染者数は10人で、ワクチン接種後の感染者はワクチン未接種の感染者に比べ、発熱した者の割合が有意に低かった（オッズ比0.113、95%信頼区間0.022-0.661）。本調査より、ワクチン接種による医療従事者のCOVID-19発症予防が確認され、ワクチン接種の有効性が示唆された。一方、ワクチン接種者がCOVID-19に罹患した場合は症状が軽微であり、COVID-19流行下においては、医療従事者は軽微な症状でも就業を停止し、COVID-19の検査を受けるべきである。
Coronavirus disease 2019 (COVID-19) is currently a serious worldwide public health crisis. As an educational and research institute that provides medical services, it is important for Keio University to maintain measures against COVID-19. Medical institutions are at particularly high risk for COVID-19 outbreaks. Therefore, precautions against such outbreaks for healthcare workers (HCWs) are vital. To consider appropriate measures against COVID-19 for HCWs, we conducted a survey of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection with approximately 4,000 HCWs (students and faculty of Keio University School of Medicine and HCWs of Keio University Hospital) from October 2020 to October 2021. We collected the clinical information of the HCWs infected with SARS-CoV-2 and analyzed the transition of infection numbers and the clinical characteristics of infected individuals. Seventy-four HCWs were infected with SARS-CoV-2. In Tokyo, infection rates among 20–50-year olds were high in the months of January (28,116), May (16,115), and August (98,364). The number of HCWs infected with SARS-CoV-2 for the same months was 13, 1, and 22 in January, May, and August, respectively. In March 2021, the applicants of HCWs received the COVID-19 vaccination. After April, among the 37 infected HCWs, 25 had received the vaccination while 12 HCWs had never received it. Nine vaccinated and ten unvaccinated HCWs had SARS-CoV-2 infection with fever. Fever occurred less frequently among the vaccinated HCWs participants as compared with the unvaccinated HCWs (Odds ratio 0.113, 95% confidence interval, 0.022–0.661). These results indicated that the COVID-19 vaccine was effective for the prevention of COVID-19 development among HCWs. However, the vaccinated HCWs with SARS-CoV-2 infection had mild symptoms, suggesting that even with mild symptoms, HCWs should excuse themselves from work and receive screening for SARS-CoV-2 infection during the COVID-19 pandemic.