COVID-19 Transmission at Schools in Japan

COVID-19 Transmission at Schools in Japan

Tetsuya Akaishi,¹ Shigeki Kushimoto,² Yukio Katori,³ Noriko Sugawara,⁴ Kaoru Igarashi,⁵ Motoo Fujita,⁶ Shigeo Kure,⁴ Shin Takayama,¹ Michiaki Abe,¹ Junichi Tanaka,¹ Akiko Kikuchi,¹ Yoshiko Abe,¹ Hiroyuki Imai,⁷ Yohei Inaba,⁸ Yoko Iwamatsu-Kobayashi,⁹ Takashi Nishioka,¹⁰ Ko Onodera¹¹ and Tadashi Ishii¹

¹Department of Education and Support for Regional Medicine, Tohoku University Hospital, Sendai, Miyagi, Japan
²Division of Emergency and Critical Care Medicine, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan
³Department of Otolaryngology-Head and Neck Surgery, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan
⁴Department of Pediatrics, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan
⁵Division of Craniofacial Anomalies, Tohoku University Graduate School of Dentistry, Sendai, Miyagi, Japan
⁶Department of Emergency and Critical Care Medicine, Tohoku University Hospital, Sendai, Miyagi, Japan
⁷Clinical Skills Laboratory, Tohoku University School of Medicine, Sendai, Miyagi, Japan
⁸Department of Radiation Disaster Medicine, International Research Institute of Disaster Science, Tohoku University, Sendai, Miyagi, Japan
⁹Department of Dental Infection Control, Tohoku University Hospital, Sendai, Miyagi, Japan
¹⁰Liaison Center for Innovative Dentistry, Tohoku University Graduate School of Dentistry, Sendai, Miyagi, Japan
¹¹Department of General Practitioner Development, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan

The coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), remains a global public health concern in 2021. However, the risk of attending schools during the pandemic remains unevaluated. This study estimated the secondary transmission rate at schools using the results of a real-time reverse transcription-polymerase chain reaction (RT-PCR) screening test performed between July 2020 and April 2021, before starting the nationwide mass vaccination. A total of 1,924 students (20 RT-PCR-positive; 1.0%) from 52 schools or preschools were evaluated, together with 1,379 non-adults (95 RT-PCR-positive; 6.9%) exposed to SARS-CoV-2 in non-school environments. Assuming that the infectious index cases were asymptomatic and the transmission at schools followed a Bernoulli process, we estimated the probability of transmission after each contact at school as approximately 0.005 (0.5% per contact) with the current infection prevention measures at schools in Japan (i.e., hand hygiene, physical distancing, wearing masks, and effective ventilation). Furthermore, assuming that all children are capable of carrying the infection, then contact between an index case and 20-30 students per day at schools would yield the expected value for secondary cases of ≥ 1.0, during the 10 days of the infectious period. In conclusion, with the current infection prevention measures at schools in Japan, secondary transmission at schools would occur in approximately every 200 contacts. When considering this rate, compliance with the current infection prevention measures at schools and early detection and quarantine of the index cases would be effective in preventing the spread of COVID-19 at schools.

Keywords —— asic reproduction number; coronavirus disease 2019 (COVID-19); school; severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2); transmission model

===============================

Tohoku J. Exp. Med 2021, 255, 239-246.

Correspondence: Tetsuya Akaishi, M.D., Ph.D., Department of Education and Support for Regional Medicine, Tohoku University Hospital, 1-1 Seiryo-machi Aoba-ku, Sendai, Miyagi 980-8574, Japan.

e-mail: t-akaishi@med.tohoku.ac.jp