Modelling the adjustment of COVID-19 response and exit from dynamic zero-COVID in China
Authors: Leung Kathy , Leung Gabriel M. , Wu Joseph T. 
Published: December 2022

AbstractBackgroundSince the initial Wuhan outbreak, China has been containing COVID-19 outbreaks through its “dynamic zero-COVID” policy. Striking a balance between sustainability and cost-benefit, China has recently begun to adjust its COVID-19 response strategies, e.g. by announcing the “20 measures” on 11 November and further the “10 measures” on 7 December 2022. Strategies for safely exiting from dynamic zero-COVID (i.e. without catastrophically overburdening health systems and/or incurring unacceptably excessive morbidity and mortality) are urgently needed.MethodsWe use simulations to assess the respective and combined effectiveness of fourth-dose heterologous boosting, large-scale antiviral treatment and public health and social measures (PHSMs) that might allow China to further adjust COVID-19 response and exit from zero-COVID safely after 7 December 2022. We also assess whether local health systems can cope with the surge of COVID-19 cases posed by reopening, given thatchunyun, a 40-day period with extremely high mobility across China associated with Spring Festival, will begin on 7 January 2023.FindingsReopening against Omicron transmission should be supported by the following interventions: 1) fourth-dose heterologous boosting 30-60 days before reopening by vaccinating 4-8% of the population per week with ≥85% uptake across all ages; 2) timely antiviral treatment with ≥60% coverage; 3) moderate PHSMs to reduce transmissibility by 47-69%. With fourth-dose vaccination coverage of 85% and antiviral coverage of 60%, the cumulative mortality burden would be reduced by 26-35% to 448-503 per million, compared with reopening without any of these interventions. Simultaneously reopening all provinces under current PHSMs would still lead to hospitalisation demand that are 1.5-2.5 times of surge hospital capacity (2.2 per 10,000 population per day).InterpretationAlthough the surge of disease burden posed by reopening in December 2022 – January 2023 would likely overload many local health systems across the country, the combined effect of vaccination, antiviral treatment and PHSMs could substantially reduce COVID-19 morbidity and mortality as China transits from dynamic-zero to normality. Planning for such a nationwide, coordinated reopening should be an urgent priority as part of the global exit from the acute phase of the COVID-19 pandemic.FundingCOVID-19 Vaccines Evaluation Program, Chinese Center for Disease Control and Prevention; Health and Medical Research Fund, Health Bureau, The Government of the Hong Kong SAR; General Research Fund, Research Grants Council, Hong KongResearch in contextEvidence before this studyWe searched PubMed and preprint archives for articles published up to 7 December 2021, that contained information about exit strategies of zero-COVID or reopening in China after the emergence of Omicron using the terms “China”, “Omicron”, “B.1.1.529”, “COVID-19”, “SARS-CoV-2”, “vaccin*”, “vaccine”, “antiviral”, “control measures”, “non-pharmaceutical intervention”, “public health and social measure”, “zero-COVID”, “exit strategy” and “reopen*”. We only found one study by Wang et al (doi: 10.1101/2022.05.07.22274792) but they assessed the feasibility of sustaining SARS-CoV-2 containment with zero-COVID strategy in China. To our knowledge, there is no discussion of exit strategies of the zero-COVID strategy or assessment of feasibility of reopening in China.Added value of this studyReopening against Omicron transmission should be supported by the following interventions: 1) fourth-dose heterologous boosting 30-60 days before reopening by vaccinating 4-8% of the population per week with ≥85% uptake across all ages; 2) timely antiviral treatment with ≥60% coverage; 3) moderate PHSMs to reduce transmissibility by 47-69%. With fourth-dose vaccination coverage of 85% and antiviral coverage of 60%, the cumulative mortality burden would be reduced by 26-35% to 448-503 per million, compared with reopening without any of these interventions. Simultaneously reopening all provinces under current PHSMs would still lead to hospitalisation demand that are 1.5-2.5 times of surge hospital capacity (2.2 per 10,000 population per day).Implications of all the available evidenceAlthough the surge of disease burden posed by reopening in December 2022 – January 2023 would likely overload many local health systems across the country, the combined effect of vaccination, antiviral treatment and PHSMs could substantially reduce COVID-19 morbidity and mortality as China transits from dynamic-zero to normality. Planning for such a nationwide, coordinated reopening should be an urgent priority as part of the global exit from the acute phase of the COVID-19 pandemic.