Consequences of abolishing the COVID-19 zero-tolerance policy in Shanghai: Lessons for future responses

To combat severe acute respiratory syndrome coronavirus 2 (SARS-Cov2), various approaches have been adopted internationally, leading to ongoing debate as to the most effective management strategy. Chinese authorities abolished the dynamic-zero approach on 7 December 2022. The authorities downgraded the COVID-19 virus into a second-level dangerous pathogen, abolished the zero-COVID policy and encouraged people to resume normal social activities. Moreover, the authorities encouraged the most vulnerable people to be vaccinated to boost their immunity and in an attempt to quickly reduce the number of acute infectious cases. As a result of these changes, over the following two months, 80% of the Chinese population were newly infected with COVID-19, probably facilitated by poor host immunity due to restrictive lockdowns over the previous three years. Vaccination rates at the time of change in the COVID-19 policy were >90% and 85% for the first and second doses, respectively, of the Sinopharm, Sinovac or CanSinoBio vaccines, excluding children aged