Reinfection rate and disease severity of the BA.5 Omicron SARS-CoV-2 lineage compared to previously circulating variants of concern in the Canary Islands (Spain)

ABSTRACT

The emergence of the Omicron SARS-CoV-2 variant of concern has changed the COVID-19 scenario as this variant is characterized by high transmissibility and immune evasion ability. To evaluate the impact of this variant on the Canary Islands (Spain) population, we determined the reinfection rates and disease severity associated with the Omicron sublineages and the previously circulating variants of concern. We performed a retrospective observational study on 21,745 SARS-CoV-2 viral genomes collected from December 2020 to July 2022 in the Canary Islands (Spain). We compared the reinfection rates between lineages using pairwise proportion and Fisher’s exact tests. To assess disease severity, we studied the association of Alpha, Delta, BA.1, BA.2, BA.5, and other risk factors on 28-day hospital mortality using logistic regression and Cox proportional hazard models. We observed 127 bona fide reinfection cases throughout the study period. We found that BA.5 had the highest reinfection rate compared to other lineages (vs. Delta p = 2.89 × 10 ⁻²⁵; vs. BA.1 p = 5.17 × 10 ⁻¹¹; vs. BA.2 p = 0.002). Among the 1,094 hospitalized patients, multivariate logistic regression showed that Alpha (Odds Ratio [OR] =  0.45, 95% Confidence Interval [CI] =  0.23-0.87, p = 0.02), BA.2 (OR =   0.38, 95% CI = 0.22-0.63, p = 1.91 × 10 ⁻⁴), and BA.5 (OR =  0.30, 95% CI = 0.16-0.55, p = 1.05 × 10 ⁻⁴) had lower 28-day hospital mortality compared to Delta. These results were confirmed by using Cox proportional hazard models. Omicron lineages, and in particular BA.5, were associated with higher reinfection rates and lower disease severity (28-day hospital mortality) than previously circulating variants of concern.