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1.
Preprint Dans Anglais | medRxiv | ID: ppmedrxiv-21266109

Résumé

The rapid spread of the SARS-CoV-2 Variant of Concern (VOC) Gamma during late 2020 and early 2021 in Brazilian settings with high seroprevalence raised some concern about the potential role of reinfections in driving the epidemic. Very few cases of reinfection associated with the VOC Gamma, however, have been reported. Here we describe 25 cases of SARS-CoV-2 reinfection confirmed by real-time RT-PCR twice within months apart in Brazil. SARS-CoV-2 genomic analysis confirmed that individuals were primo-infected between March and December 2020 with distinct viral lineages, including B.1.1, B.1.1.28, B.1.1.33, B.1.195 and P.2, and then reinfected with the VOC Gamma between 3 to 12 months after primo-infection. The overall mean cycle threshold (Ct) value of the first (25.7) and second (24.5) episodes were roughly similar for the whole group and 14 individuals displayed mean Ct values < 25.0 at reinfection. Sera of 14 patients tested by plaque reduction neutralization test after reinfection displayed detectable neutralizing antibodies against Gamma and other SARS-CoV-2 variants (B.1.33, B.1.1.28 and Delta). All individuals have milder or no symptoms after reinfection and none required hospitalization. The present study demonstrates that the VOC Gamma was associated with reinfections during the second Brazilian epidemic wave in 2021 and raised concern about the potential infectiousness of reinfected subjects. Although individuals here analyzed failed to mount a long-term sterilizing immunity, they developed a high anti-Gamma neutralizing antibody response after reinfection that may provide some protection against severe disease.

2.
Preprint Dans Anglais | medRxiv | ID: ppmedrxiv-21266251

Résumé

The SARS-CoV-2 Variant of Concern (VOC) Delta was first detected in India in October 2020. The first imported cases of the Delta variant in Brazil were identified in April 2021 in the Southern region, followed by more cases in different country regions during the following months. By early September 2021, Delta was already the dominant variant in the Southeastern (87%), Southern (73%), and Northeastern (52%) Brazilian regions. This work aimed to understand the spatiotemporal dissemination dynamics of Delta in Brazil. To this end, we employed a combination of Maximum Likelihood (ML) and Bayesian methods to reconstruct the evolutionary relationship of 2,264 of VOC Delta complete genomes (482 from this study) recovered across 21 out of 27 Brazilian federal units. Our phylogeographic analyses identified three major transmission clusters of Delta in Brazil. The clade BR-I (n = 1,560) arose in Rio de Janeiro in late April 2021 and was the major cluster behind the dissemination of the VOC Delta in the Southeastern, Northeastern, Northern, and Central-Western regions. The clade BR-II (n = 207) arose in the Parana state in late April 2021 and aggregated the largest fraction of sampled genomes from the Southern region. Lastly, the clade BR-III emerged in the Sao Paulo state in early June 2021 and remained mostly restricted to this state. In the rapid turnover of viral variants characteristic of the SARS-CoV-2 pandemic, Brazilian regions seem to occupy different stages of an increasing prevalence of the VOC Delta in their epidemic profiles. This process demands continuous genomic and epidemiological surveillance toward identifying and mitigating new introductions, limiting their dissemination, and preventing the establishment of more significant outbreaks in a population already heavily affected by the COVID-19 pandemic.

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