Dynamic Evolution Characteristics of SVEIR Model With Variants and Non-Pharmaceutical Interventions for Controlling COVID-19

The epidemiological characteristics and distributions of two epidemics in Fujian Province of Southeast China were attributed to the complex interactions among variant, host, and non-pharmaceutical intervention. All reported cases of Putian epidemic (September 8--October 2, 2021, Delta variant B.1.617.2) and Fuzhou epidemic (October 22--November 18, 2022, Omicron variant BA.5.2) were classified by gender, age group, occupation, and location in this paper. By the surveillance data from Fujian Provincial Center for Disease Control and prevention, we established an virus-oriented SVEIR model to investigate the dynamic evolution features for two variants. The optimal simulations by Least Square were operated with distinct variant and scenario investigation. The comparisons from scenario investigations showed that non-pharmaceutical interventions significantly reduced infection scales of COVID-19 epidemic, and that Omicron variant was more infectious than Delta variant. The estimation of the basic reproduction number showed that R0 of Putian epidemic was 3.90, and the effective reproduction number Rt was below 1 on September 20, 2021; R0 of Fuzhou epidemic was 7.80, and Rt was below 1 on November 5, 2022. Moreover, the dynamic investigations provided that the increasing tendencies were verified from Delta variant to Omicron variant, such as the basic reproduction number, the infection rate, the percentage of high-risk cases and the growth rate. Meanwhile, the decreasing tendencies were also identified such as the average recovery period, the awareness delay and the percentage of symptomatic cases. This study also pointed out age group profile was the important index during the transmission of COVID-19, and that non-pharmaceutical interventions of two epidemics played critical rules to successfully contain, which were strongly recommended to public health policy makers.