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BackgroundOmicron, 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.MethodsIn this retrospective study, we compared the strictness of government lockdown policies in Shanghai and some countries. Based on the daily Omicron case number from March 1st 2022 to April 30th 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.ResultsAfter 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 carrier than the symptomatic cases.ConclusionsThe strict lockdown could curb the transmission of Omicron effectively, especially for the asymptomatic spread. And urban city with extensive personnel movement is suggested to adopt this lockdown strategy at early stage to maximally control the virus transmission.