AUTHOR=Qian Ying , Cao Siqi , Zhao Laijun , Yan Yuge , Huang Jiaoling 

TITLE=Policy choices for Shanghai responding to challenges of Omicron

JOURNAL=Frontiers in Public Health

VOLUME=Volume 10 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/public-health/articles/10.3389/fpubh.2022.927387

DOI=10.3389/fpubh.2022.927387

ISSN=2296-2565

ABSTRACT=Background: A new wave of COVID-19 infection driven by Omicron BA.2 subvariant hit Shanghai end of February 2020. With higher transmissibility and milder symptoms, the daily new confirmed cases have soared to more than 20K within one and a half months. The greatest challenge of Omicron spreading is that the rapidly surging number of infected population overwhelming the healthcare system. What policy is effective for huge cities to fight against fast spreading COVID-19 new variant remains a question.
Methods: A system dynamics model of Shanghai Omicron epidemic was developed as an extension of the traditional SEIR model to incorporate the policies, such as contact tracing and quarantine, COVID-19 testing, isolation of areas concerned, and vaccination. Epidemic data from Shanghai Municipal Health Commission were collected for model validation.
Results: Three policies were tested with the model: COVID-19 testing, isolation of areas concerned and vaccination. Maintaining high level of COVID-19 testing and transfer rate of the infected population can prevent the number of daily new confirmed cases from recurring growth. In the scenario that 50% of the infected population could be transferred for quarantine on daily bases, the daily confirmed asymptomatic cases and symptomatic cases remained at low level under 100. For isolation of areas concerned, in the scenario with most isolation scope, the peak of daily confirmed asymptomatic and symptomatic cases dropped 18% and 16% respectively compared with that in the scenario with least isolation. Regarding vaccination, increasing the vaccination rate from 75% to 95% only slightly reduced the peak of the confirmed cases, but it can reduce the severe cases and death for 170%.   
Conclusions: The effective policies for Omicron include high level of testing capacity with a combination of RAT and PCR testing to identify and quarantine the infected cases, especially the asymptomatic cases. Immediate home-isolation and fast transfer to centralized quarantine location could help control the spread of the virus. Moreover, promote the vaccination in vulnerable population could significantly reduce the severe cases and death. These policies could be applicable to all metropolis with huge population facing high transmissible low severity epidemic.