The Effect of Strict Lockdown on Omicron SARS-CoV-2 Variant Transmission in Shanghai

Abstract

Omicron, the current SARS-CoV-2 variant of concern, is much more contagious than other previous variants. Whether strict lockdown could effectively curb the transmission of Omicron is largely unknown. In this retrospective study, we compared the strictness of government lockdown policies in Shanghai and other countries. Based on the daily Omicron case number from 1 March 2022 to 30 April 2022, the effective reproductive numbers in this Shanghai Omicron wave were calculated to confirm the impact of strict lockdown on Omicron transmission. Pearson correlation was conducted to illustrate the determining factor of strict lockdown outcomes in the 16 different districts of Shanghai. After a very strict citywide lockdown since April 1st, the average daily effective reproductive number reduced significantly, indicating that strict lockdown could slow down the spreading of Omicron. Omicron control is more challenging in districts with higher population mobility and lockdown is more likely to decrease the number of asymptomatic carriers than the symptomatic cases. All these findings indicate that the strict lockdown could curb the transmission of Omicron effectively, especially for the asymptomatic spread, and suggest that differentiated COVID-19 prevention and control measures should be adopted according to the population density and demographic composition of each community.

Retrospective Modeling of the Omicron Epidemic in Shanghai, China: Exploring the Timing and Performance of Control Measures

“…Several studies have comprehensively described the epidemiological characteristics, spatiotemporal transmission dynamics, or disease burden of the Omicron outbreak under the population-based screening and lockdown policies implemented in Shanghai [ 24 , 25 ]. There are also some studies that have predicted the Shanghai epidemic situation or have evaluated policy effects through modeling [ 26 , 27 , 28 ]. However, none of these studies have explored the timing and performance of control measures.…”

Quantitative analysis of non-pharmaceutical interventions during Shanghai COVID-19 outbreak

“…pl,t is the local optimal solution of this particle found until time t, and pg,t represents the global optimal solution of the whole swarm found until time t. c1, c2, c3 are recognition coefficients, and r1, r2 are the random parameters within[0,1]. Each iteration updates the velocity and position of particles according to equation (6) (7). When the number of iterations reaches a preset maximum value, the algorithm terminates and outputs the optimized result.…”

“…Zhiyuan Chen et al conducted in-depth descriptive research on epidemic characteristics and spatiotemporal transmission dynamics, and analyzed the trend of Rt and the characteristics of spatial-temporal transmission of the virus [6]. Haibo Yang et al used stringency index of Shanghai lockdown combined with the effective reproductive number and effective interval to study the effect of strict lock down [7]. Tao Dong et al constructed an agent-based model using geographic information system and real population data and used the model to simulate the spread of virus in Huangpu District from March 8 to June 15, 2022 [8].…”

A mini review of reinfection with the SARS‐CoV‐2 Omicron variant

“…Since the first identification of severe pneumonia with COVID‐19 in 2019, 1 there have been over 768 million confirmed cases and more than 6.9 million deaths reported (WHO, June 21, 2023). China's stringent lockdown, quarantine policy, and mass testing before December 2022 2,3 resulted in a lower prevalence of confirmed and asymptomatic cases compared to other countries 4,5 . Following the end of the dynamic zero‐COVID policy, the incidence of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) has soared, and concerns about reinfection have arisen 6,7 .…”