In March 2023, XBB accounted for 83.3% of SARS-CoV-2 cases in Rio Grande do Sul, Brazil.
143 samples were identified as XBB, while 586 were classified as other Omicron lineages.
97.7% of patients infected with XBB recovered, with a low mortality rate of 2.3%.
59.5% of previously infected and vaccinated patients experienced reinfection with XBB.
54% of individuals had an interval of over one year since their last vaccine dose before XBB infection.
90 mutations associated with immune resistance were identified in the XBB lineage, particularly in the Spike protein region.
Simplified
The COVID-19 pandemic has been marked by novel viral variants, posing challenges to global public health. , a viral evolution mechanism, is implicated in SARS-CoV-2's ongoing evolution. The XBB recombinant lineage, known for evading antibody-mediated immunity, exhibits higher transmissibility without increased disease severity. We investigated the prevalence and genomic features of XBB in SARS-CoV-2-positive cases in Rio Grande do Sul (RS), Brazil. We sequenced 357 samples from epidemiological weeks (EW) 47/2022 to 17/2023, and included 389 publicly available sequences. Clinical and epidemiological data were obtained from DATASUS, e-SUS, and SIVEP GRIPE (data recording systems of the Brazilian Ministry of Health). Of these, 143 were classified as XBB and 586 were other Omicron lineages. In March 2023 (EW 10), XBB became dominant, accounting for 83.3% of cases. 97.7% of XBB-infected patients successfully recovered from the infection, with a low mortality rate (2.3%). Even after receiving three vaccine doses and having been previously infected, 59.5% of the patients experienced reinfection with XBB. However, for 54% of the individuals, the interval between their XBB infection and the last vaccine dose exceeded one year, potentially leading to a decline in antibody levels. In addition, we identified 90 mutations in RS circulating XBB, spread throughout the genome, notably in the Spike protein region associated with immune resistance. This study provides insights into the dynamics and impact of a recombinant variant becoming predominant for the first time in the state. Continued surveillance of SARS-CoV-2 genomic evolution is crucial for effective public health management.
Key numbers
83.3%
Dominance of XBB
Percentage of SARS-CoV-2 cases attributed to XBB in March 2023.
59.5%
Reinfection Rate
Percentage of individuals reinfected with XBB among those previously infected.
90
Mutation Count
Total mutations found in the XBB genome.
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