![]() ![]() ![]() In this article, we compared the strictness of Shanghai lockdown policy with that of other countries. Thus, lockdown measures may still be needed facing Omicron wave but its effect remains largely unknown. Furthermore, Omicron displays key mutations associated with immune escape (K417N, E484A, T478K in the RBD), forcing researchers to develop novel vaccines for Omicron as the vaccines previously administered to the public are not ideal anymore 10. However, the epidemiology study of the Hong Kong Omicron wave in early 2022 revealed that the intrinsic severity of Omicron may not be much lower than the ancestral strains 9. Another important observation in the Omicron epidemic is the reduced odds of hospital admission for patients, which then becomes an implication for the relaxation of public health and social measures (PHSM) as chosen by most of the countries 8. These changes render the Omicron variant a short mean serial interval of 3 days and an assumed R0 as high as 10 6, 7. In detail, the significant number of mutations in the SARS-CoV-2 receptor-binding domain (RBD) render the Omicron variant a higher affinity for human angiotensin-converting enzyme 2 than the Delta variant. This change suggests a strong selective advantage of Omicron as proven by further mutational profile study 5. It caused abrupt epidemic outbreaks across South Africa, then Europe, and eventually the rest of the world by outcompeting Delta VOC, which accounted for at least 90% of genomes sequenced globally in October 2021 4. On November 2 nd 2021, the novel SARS-CoV-2 VOC Omicron was first collected in South Africa and then spread rapidly. Even though vaccines from Pfizer, Moderna, Sinopharm and other companies were later listed by WHO for emergency use, the emergence of new Variant of Concern (VOC) such as Delta drove a number of SARS-CoV-2 waves and lockdown was still implemented by the majority of governments from time to time 3. As there were none available vaccines and drugs at first, all the countries relied on non-pharmaceutical interventions and applied lockdown strategy in 2020 as the critical prevention and control measure 2. Since December 2019, COVID-19 outbreak suddenly and rapidly spread all over the world 1. ![]()
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