Shanghai’s life-saving efforts against the current omicron wave of the COVID-19 pandemic

In late February, 2022, a wave of SARS-CoV-2 infection rapidly appeared in Shanghai, China. According to the Shanghai Municipal Health Commission, as of May 4, 2022, 601,942 cases have been identified, including 547,056 asymptomatic carriers. 503 people have died with or from COVID-19. Phylogenetic features of SARS-CoV-2 viral genomes from 129 patients in this period, and inferring their relationship with those available on the GISAID database, indicated that all of the new viral genomes in Shanghai were clustered into the SARS-CoV-2 BA. 2.2 sublineage. Of note, BA.2 is a sub-lineage of the omicron variant of SARS-CoV-2 (B.1.1.159). Multiple sub-lineages of BA.2 have been characterised, many of which appear to show distinct regional distribution patterns. At present, BA2.2 only represents a small sub-lineage of BA.2 worldwide (1993 [0·25%] of 800 366 sequences in GISAID), sequences of which have been detected in Hong Kong (839 [42·10%]), the UK (742 [37·20%]), and Australia (121 [6·10%]). We assessed the potential risk of various feature mutations on BA2.2 on the severity of COVID-19 and found that these mutations showed no significance in their distributions between severe to critical and mild to moderate COVID-19, suggesting that the observed disease severity is probably mainly attributed to comorbidities.

Although omicron BA.2 evolves towards less virulent, a higher rate of severe outcomes and considerable mortality have been reported in unvaccinated people, especially older adults.

Lessons learned from the fifth wave of COVID-19 in Hong Kong in early 2022.