ABSTRACT
Background: The second wave of the coronavirus disease 2019 (COVID-19) epidemic in India was caused by the COVID-19 Delta variant. However, the epidemiological characteristics and transmission mechanism of the Delta variant remain unclear. To explore whether the epidemic trend will change after effective isolation measures were taken and what is the minimum number of individuals who need to be vaccinated to end the epidemic. Methods: We used actual data from March 5 to April 15, 2021, of daily updates confirmed cases and deaths, to estimate the parameters of the model and predict the severity of possible infection in the coming months. The classical Susceptible-Exposed-Infected-Removed (SEIR) model and extended models [Susceptible-Exposed-Infected-Removed-Quarantine (SERIQ) model and Susceptible-Exposed-Infected-Removed- medicine (SERIM) model] were developed to simulate the development of epidemic under the circumstances of without any measures, after effective isolation measures were taken and after being fully vaccinated. Results: The result demonstrated good accuracy of the classic model. The SEIRQ model showed that after isolation measures were taken, the infections will decrease by 99.61% compared to the actual number of infections by April 15. And the SEIRQ model demonstrated that if the vaccine efficative rate was 90%, when the vaccination rate was 100%, the number of existing cases would reach a peak of 529,723 cases on the 52nd day. Conclusion: Effective quarantine measures and COVID-19 vaccination from official are critical prevention measures to help end the COVID-19 pandemic.
Subject(s)
COVID-19ABSTRACT
Background: The initial outbreak of coronavirus disease 2019 (COVID-19) pandemic has rapidly extended globally, which brought huge detrimental to the whole society. While some countries and regions are currently experiencing another outbreak of COVID-19.Methods: In this study, by using the epidemic data from January 2 to February 11, 2021 in city Shijiazhuang, an extended SEIR model was established to evaluate the effectiveness of emergency response, nucleic acid testing (NAT) and stay-at-home order for all individuals, and to simulate the impact of delayed interventions.Findings: We estimated an initial effective reproduction number (Rt) was 4·70, and the Rt value gradually decreased with the implementation of government interventions. Meanwhile, the final cumulative number of confirmed cases decreased by 99·99% (898 cases), and peak of current confirmed cases decreased by 99·99% (763 cases) compared with that without intervention. With fewer interventions, the number of infected individuals will continue to increase. Delayed interventions were simulated which would show at least 80% (1614 cases), 218% (2854 cases), 464% (5061 cases), and 879% (8787 cases) more infections can be attained for Shijiazhuang city, if the intervention was delayed by 2, 4, 6, and 8 days, respectively.Interpretation: The Shijiazhuang government has effectively controlled the spread of the epidemic by adopting a series of comprehensive non-pharmacological interventions in time.Funding Information: The study was supported by grants from the National Social Science Foundation of China (20BRK041).Declaration of Interests: The authors declare that they have no competing interests.