Clinical severity of Omicron subvariants BA.1, BA.2, and BA.5 in a population‐based cohort study in British Columbia, Canada

Abstract

The SARS‐CoV‐2 variant Omicron emerged in late 2021. In British Columbia (BC), Canada, and globally, three genetically distinct subvariants of Omicron, BA.1, BA.2, and BA.5, emerged and became dominant successively within an 8‐month period. SARS‐CoV‐2 subvariants continue to circulate in the population, acquiring new mutations that have the potential to alter infectivity, immunity, and disease severity. Here, we report a propensity‐matched severity analysis from residents of BC over the course of the Omicron wave, including 39,237 individuals infected with BA.1, BA.2, or BA.5 based on paired high‐quality sequence data and linked to comprehensive clinical outcomes data between December 23, 2021 and August 31, 2022. Relative to BA.1, BA.2 cases were associated with a 15% and 28% lower risk of hospitalization and intensive care unit (ICU) admission (aHRhospital = 1.17; 95% confidence interval [CI] = 1.096–1.252; aHRICU = 1.368; 95% CI = 1.152–1.624), whereas BA.5 infections were associated with an 18% higher risk of hospitalization (aHRhospital = 1.18; 95% CI = 1.133–1.224) after accounting for age, sex, comorbidities, vaccination status, geography, and social determinants of health. Phylogenetic analysis revealed no specific subclades associated with more severe clinical outcomes for any Omicron subvariant. In summary, BA.1, BA.2, and BA.5 subvariants were associated with differences in clinical severity, emphasizing how variant‐specific monitoring programs remain critical components of patient and population‐level public health responses as the pandemic continues.

Incidence and severity of SARS‐CoV‐2 reinfection, a multicenter cohort study in Shanghai, China

“…24 Our study reported higher severity among primary infections during the circulation of BA.5 sublineages than primary infections during the circulation of BA.2. This corresponds to the result of a populationbased cohort study in Canada that BA.5 was more severe than BA.1 and BA.2 with higher risk of hospitalization, 25 and a Korean prospective cohort study that BA.5 was associated with more severe and frequent systemic symptoms than BA.1 and BA.2. 26 To note, patients infected during the second Omicron wave in Shanghai had higher levels of viral exposure compared to those infected during the first wave, which might add to severer symptoms other than different pathogenicity of subvariants.…”

Genomic Surveillance of SARS-CoV-2 Variants in the Dominican Republic and Emergence of a Local Lineage

“…The Omicron variant and subvariants have been demonstrated to be more immunologically evasive and environmentally persistent than the ancestral strains. The high rate of mutation and increased infectivity will be challenging for surveillance systems worldwide [ 68 , 69 , 70 , 71 , 72 , 73 , 74 ].…”

SARS-CoV-2 Omicron variants BA.4 and BA.5 dominated the fifth COVID-19 epidemiological wave in Mexico

“…Compared to the BA.2 spike protein, the BA.4 and BA.5 sequences contain two additional amino acid changes (L452R and F486V), one deletion (69-70del) and one reversion (R493Q). These two variants were shown to have a higher infection rate in vaccinated or previously infected people [16, 22, 23] and a higher risk of hospitalization relative to BA.1 [10, 24].…”