Rapid development of an updated mRNA vaccine against the SARS-CoV-2 Omicron variant

Dear Editor, Since the declaration of public Health Emergency of Interna-tional Concern(PHEIC)by the WHO,the COVID-19 pandemic,caused by the severe acute respiratory syndrome coronavirus 2(SARS-CoV-2),has led to over 300 million confirmed cases with more than 5 million deaths in the past 2 years.On top of that,SARS-CoV-2 continues evolving into many variants,and many of these variants with evidence to enhance viral transmissibility,adaptiveness,infectivity,and/or to escape from host immune response are classified as variants of concerns(VOC).1 Since the outbreak of the pandemic,five VOCs,including Alpha,Beta,Gamma,Delta,and Omicron have been verified by the WHO.