Objective To describe a COVID-19 outbreak due to SARS-CoV-2 Omicron variant in a school and provide suggestions for COVID-19 prevention and control.

Methods Data on the COVID-19 outbreak in a school in Putuo District of Shanghai were collected from November 14 to December 20， 2022. Epidemiological characteristics， incidence rate of secondary cases and response measures were described and analyzed.

Results A total of 27 COVID-19 cases were identified infected with SARS-CoV-2 Omicron BA.5.2 variant， including 14 students （51.9%） and 13 family members / teachers living with those students （48.1%）. The first case occurred on November 14， with peak incidence during November 16-18. The median generation interval of the second generation cases was 2 （2，3） days. The index case （case 1， a student） had a clear contact history outside the school， which was found through routine examination in key populations in the school. Immediate management was conducted after the notification. All the second generation cases were exposed students in the same class with case 1， which were identified during the quarantine， whereas the third generation cases were their family members/teachers living with the second generation cases. The incidence rate within the class and school were 36.8% and 3.0%， respectively. No further social transmission was found outside the school.

Conclusion Early detection， multi-sectoral collaboration， prompt control and quarantine measures are effective in containing SARS-CoV-2 transmission. Health promotion， surveillance， ventilation and prophylactic disinfection should be reinforced in schools， office buildings and other gathering places.