space traveling warriors tier list : Comparison of the stringency of Shanghai’s lockdown policy with that of other countries

In a recent study published in medRxiv* preprint server, researchers investigated whether strict lockdowns could effectively reduce transmission of the Omicron variant of severe acute respiratory syndrome 2 (SARS-CoV-2) in Shanghai.

Studying: The effect of strict blocking on transmission of the Omicron variant SARS-CoV-2 in Shanghai. Image credit: Graeme Kennedy/Shutterstock

Background

The high transmissibility and enhanced immune evasion of Omicron, along with the lack of vaccines targeting Omicron, justify the need for lockdowns. On March 1, 2022, Omicron BA.2 infections were first reported in Shanghai. The daily count of infections increased rapidly in subsequent weeks, due to which, on March 28, the Shanghai government implemented a lockdown in the eastern regions of Shanghai, and later a city-wide lockdown on April 1 to control the spread. of Omicron.

about the study

In the present retrospective study, researchers investigated the effectiveness of strict lockdown measures implemented in Shanghai to contain Omicron transmission.

Based on daily Omicron infection counts between March 1, 2022 and April 30, 2022 obtained from the Shanghai Municipal Health Commission database, Omicron effective reproductive numbers (Rt) were calculated. Correlation analysis using Pearson’s correlation coefficient was performed to correlate lockdown results in 16 districts of Shanghai, for which the infection index and active infection index were calculated.

Shanghai’s lockdown policy was divided into three stages of public health and social measures (PHSM). Phase I (between March 1 and March 12) comprised regular COVID-19 prevention and control measures with minimal restrictions. Stage II (between 13 and 31 March) was the precise stage of epidemic control where only residents of specific high-risk communities were to be quarantined. Phase III (as of April 1) comprised city-wide lockdowns.

To quantify the strictness of lockdown policies, Oxford’s coronavirus government response tracking project was followed with metrics such as school closures, workplace closures, bans on public events, restrictions on public gatherings, restrictions on indoor movement. , public transport closures, stay-at-home restrictions, domestic and international travel restrictions, and public information campaigns. After excluding public health campaigns, the stringency indices for Shanghai were calculated from the other metrics across the three steps and compared to those for the UK, US, France, Germany and other nations.

The rate of asymptomatic spread of Omicron infections was determined and trends in Omicron infection in all districts were observed. To further assess the effectiveness of the block, the period between the start date of the block and the date of the peak of Omicron infections was calculated and referred to as the effective interval (EI) of the block. In addition, the impact of the Omicron cases and population movement on EI was evaluated.

Results

The average daily Rt of stages I and II was 1.76 and 1.79, respectively, lower than the average (Rt 3.4) of South Africa, the Netherlands, India and the United Kingdom. It is important to note that the Rt was substantially lower (Rt 1.0) in stage III in Shanghai, indicating that blockages can effectively prevent Omicron transmission.

The Shanghai lockdown stringency index reached 97, slightly lower than India’s lockdowns but higher than all other countries. The daily rigor index in stage I was as low as nine, as only people with a history of travel from a medium or high risk region were being monitored. Subsequently, Shanghai began to control high-risk private communities, and the daily rigor index during stage II increased to 45 and further increased to 97 in stage III.

After the city-wide lockdown from April 1, the daily count of Omicron infections reported in Shanghai peaked on April 12, indicating an EI of 11 days, substantially lower than that of the Chinese city of Wuhan for the year. 2020 (20-day EI). Distinct EIs were reported for different districts of Shanghai ranging from six days to 20 days, with double peaks observed for districts such as Yangpu, Baoshan and Hongkou.

A positive correlation was observed between IE days and the rate of active infection, indicating that an increase in Omicron infections and a large movement of personnel are challenges in reducing Omicron transmission. Therefore, timely lockdowns before an increase in Omicron infections are essential to quickly control the spread of Omicron, particularly in densely populated urban areas.

In Shanghai, during stage I and stage II, the average rates of asymptomatic spread of Omicron infections were 94.7% and 96.8%, respectively, which reduced to 90% in stage III. Rates fluctuated above 80%, which may be due to characteristic traits of Omicron, vaccination rates, and prompt detection of Omicron infections among the masses. Rates were increased by healthy individuals younger than age 60, accounting for 85% of cases, including young individuals with active social contact and middle-aged individuals with contact restricted to family and neighborhoods sharing a kitchen and/or bathroom.

Overall, the study results showed that strict lockdowns can effectively contain the transmission of Omicron, particularly the spread of asymptomatic SARS-CoV-2 infections. Furthermore, the adoption of the lockdown strategy by densely populated urban cities in the early stages of the pandemic would provide maximum benefit in controlling the spread of Omicron.

*Important news

medRxiv publishes preliminary scientific reports that are not peer-reviewed and therefore should not be considered conclusive, guide clinical practice/health-related behavior, or treated as established information.

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