mRNA-Based Vaccine BNT162b2 Might Reduce Severe Acute Respiratory Syndrome Coronavirus 2 B.1.1.7 Variant Transmission in Japanese Population.

Coronavirus disease 2019 (COVID-19) cluster with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) B.1.1.7 variant occurred between April 10, 2021, and May 26, 2021, at Japan Community Health Care Organization (JCHO) Sapporo Hokushin Hospital in Sapporo, Japan. We found that the four infected staff members accounted for 5.3% of all 75 infected persons, approximately one of 10 the percentage of other Japanese hospitals that experienced disease clusters caused by wild-type SARS-CoV-2 until January 2021. Furthermore, none of the infected staff developed COVID-19. Nationwide vaccination began in February 2021, when wild-type SARS-CoV-2 infection remained prevalent in Japan. During March-May, Sapporo had already experienced an explosive increase in SARS-CoV-2 B.1.1.7 cases. JCHO Sapporo Hokushin Hospital started optional vaccination for staff members using BNT162b2. The first inoculations occurred between February 22, 2021, and April 28, 2021, and the second between March 15, 2021, and May 7, 2021. This is the first report that BNT162b2 might reduce B.1.1.7 variant transmission in Japanese population.