In a current examine posted to the medRxiv* preprint server, researchers investigated whether or not strict lockdowns may successfully scale back the extreme acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant transmission in Shanghai.

Study: The impact of strict lockdown on Omicron SARS-CoV-2 variant transmission in Shanghai. Image Credit: Graeme Kennedy/Shutterstock

Background

The excessive transmissibility and enhanced immune-evasiveness of Omicron coupled with the dearth of Omicron-targeted vaccines warrant the necessity for lockdowns. On 1 March 2022, Omicron BA.2 infections had been first reported in Shanghai. The every day rely of infections elevated swiftly within the subsequent weeks, resulting from which, on 28 March, the federal government of Shanghai authorities carried out a lockdown in japanese areas of Shanghai and subsequently a citywide lockdown on 1 April to manage the unfold of Omicron.

About the examine

In the current retrospective examine, researchers investigated the effectiveness of strict lockdown measures carried out in Shanghai for curbing Omicron transmission.

Based on every day counts of Omicron infections between 1 March 2022 and 30 April 2022, obtained from the Shanghai municipal health fee database, the efficient reproductive numbers (Rt) of Omicron had been calculated. Correlation evaluation utilizing the Pearson correlation coefficient was carried out to correlate the lockdown outcomes in 16 districts of Shanghai, for which the an infection index and the energetic an infection index had been calculated.

The Shanghai lockdown coverage was divided into three public health and social measures (PHSM) levels. Stage I (between 1 March and 12 March) comprised common COVID-19 prevention and management measures with minimal restrictions. Stage II (between 13 March and 31 March) was the exact epidemic management stage whereby solely residents of explicit high-risk communities had been to be quarantined. Stage III (starting 1 April) comprised citywide lockdowns.

For quantifying the stringency of lockdown insurance policies, the Oxford coronavirus authorities response tracker undertaking was adopted with metrics akin to faculty closure, office closure, prohibition of public occasions, restrictions for public gatherings, inner motion restrictions, public transport closure, keep at house restrictions, home and worldwide journey restrictions, and public info campaigns. After excluding public health campaigns, stringency indices for Shanghai had been calculated from the opposite metrics on the three levels and in comparison with these of the United Kingdom, United States, France, Germany, and different nations.

The price of asymptomatic unfold of Omicron infections was decided, and Omicron an infection developments in each district had been noticed. To additional consider the effectiveness of lockdown, the interval between the date of lockdown graduation and the date of peak in Omicron infections was calculated and known as the efficient interval (EI) of lockdown. In addition, the affect of Omicron circumstances and inhabitants motion on EI was evaluated.

Results

Daily common Rt of levels I and II had been 1.76 and 1.79, respectively, lesser than the imply (Rt 3.4) for South Africa, the Netherlands, India, and the United Kingdom. Of observe, the Rt was considerably decrease (Rt 1.0) in stage III in Shanghai, indicating that lockdowns may stop Omicron transmission successfully.

The stringency index of the Shanghai lockdown was as excessive as 97, marginally decrease than India lockdowns however increased than all different international locations. The on a regular basis stringency index in stage I used to be as little as 9 as solely individuals with medium-risk or high-risk area journey historical past had been being monitored. Subsequently, Shanghai started to manage explicit high-risk communities, and the every day stringency index throughout stage II elevated to 45 and additional elevated to 97 in stage III.

After the citywide lockdown starting on 1 April, the every day rely of Omicron infections reported in Shanghai demonstrated a peak on 12 April, indicating an 11-day EI, which was considerably shorter than that of the Wuhan metropolis of China within the yr 2020 (EI of 20 days). Distinct EIs had been reported for the completely different Shanghai districts ranging between six days and 20 days, with double peaks famous for districts akin to Yangpu, Baoshan, and Hongkou.

A optimistic correlation was noticed between EI days and the energetic an infection index, indicating that a rise in Omicron infections and intensive motion of personnel are challenges in lowering Omicron transmission. Therefore, well timed lockdowns earlier than a surge in Omicron infections are important for quickly controlling Omicron unfold, notably in population-dense city areas.

In Shanghai, throughout stage I and stage II, the median charges of asymptomatic unfold of Omicron infections had been 94.7% and 96.8%, respectively, which decreased to 90% in stage III. The charges fluctuated above 80%, which could possibly be resulting from attribute Omicron traits, vaccination charges, and immediate detection of Omicron infections among the many lots. The charges had been pushed up by wholesome people aged <60 years, accounting for 85% of circumstances, together with younger people with energetic social contact and middle-aged people with contact restricted to household and neighborhoods sharing the kitchen and/or bathroom.

Overall, the examine findings confirmed that stringent lockdowns may successfully curb Omicron transmission, notably the unfold of asymptomatic SARS-CoV-2 infections. In addition, adopting the lockdown technique by population-dense city cities within the preliminary levels of the pandemic would offer maximal profit in controlling Omicron unfold.

*Important discover

medRxiv publishes preliminary scientific stories that aren’t peer-reviewed and, subsequently, shouldn’t be considered conclusive, information scientific apply/health-related habits, or handled as established info.