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1.
Preprint Dans Anglais | medRxiv | ID: ppmedrxiv-22280193

Résumé

The SARS-CoV-2 variants of concern (VOCs) Delta and Omicron spread globally during mid and late 2021, respectively, with variable impact according to the immune population landscape. In this study, we compare the dissemination dynamics of these VOCs in the Amazonas state, one of Brazils most heavily affected regions. We sequenced the virus genome from 4,128 patients collected in Amazonas between July 1st, 2021 and January 31st, 2022 and investigated the lineage replacement dynamics using a phylodynamic approach. The VOCs Delta and Omicron displayed similar patterns of phylogeographic spread but significantly different epidemic dynamics. The Delta and Omicron epidemics were fueled by multiple introduction events, followed by the successful establishment of a few local transmission lineages of considerable size that mainly arose in the Capital, Manaus. The VOC Omicron spread and became dominant much faster than the VOC Delta. We estimate that under the same epidemiological conditions, the average Re of Omicron was [~]3.3 times higher than that of Delta and the average Re of the Delta was [~]1.3 times higher than that of Gamma. Furthermore, the gradual replacement of Gamma by Delta occurred without an upsurge of COVID-19 cases, while the rise of Omicron fueled a sharp increase in SARS-CoV-2 infection. The Omicron wave displayed a shorter duration and a clear decoupling between the number of SARS-CoV-2 cases and deaths compared with previous (B.1.* and Gamma) waves in the Amazonas state. These findings suggest that the high level of hybrid immunity (infection plus vaccination) acquired by the Amazonian population by mid-2021 was able to limit the spread of the VOC Delta and was also probably crucial to curb the number of severe cases, although not the number of VOC Omicron new infections.

2.
Preprint Dans Anglais | medRxiv | ID: ppmedrxiv-21263453

Résumé

The Amazonas was one of the most heavily affected Brazilian states by the COVID-19 epidemic. Despite a large number of infected people, particularly during the second wave associated with the spread of the Variant of Concern (VOC) Gamma (lineage P.1), SARS-CoV-2 continues to circulate in the Amazonas. To understand how SARS-CoV-2 persisted in a human population with a high immunity barrier, we generated 1,188 SARS-CoV-2 whole-genome sequences from individuals diagnosed in the Amazonas state from 1st January to 6th July 2021, of which 38 were vaccine breakthrough infections. Our study reveals a sharp increase in the relative prevalence of Gamma plus (P.1+) variants, designated as Pango Lineages P.1.3 to P.1.6, harboring two types of additional Spike changes: deletions in the N-terminal (NTD) domain (particularly{Delta} 144 or{Delta} 141-144) associated with resistance to anti-NTD neutralizing antibodies or mutations at the S1/S2 junction (N679K or P681H) that probably enhance the binding affinity to the furin cleavage site, as suggested by our molecular dynamics simulations. As lineages P.1.4 (S:N679K) and P.1.6 (S:P681H) expanded (Re > 1) from March to July 2021, the lineage P.1 declined (Re < 1) and the median Ct value of SARS-CoV-2 positive cases in Amazonas significantly decreases. Still, we found no overrepresentation of P.1+ variants among breakthrough cases of fully vaccinated patients (71%) in comparison to unvaccinated individuals (93%). This evidence supports that the ongoing endemic transmission of SARS-CoV-2 in the Amazonas is driven by the spread of new local Gamma/P.1 sub-lineages that are more transmissible, although not more efficient to evade vaccine-elicited immunity than the parental VOC. Finally, as SARS-CoV-2 continues to spread in human populations with a declining density of susceptible hosts, the risk of selecting new variants with higher infectivity are expected to increase.

3.
Preprint Dans Anglais | medRxiv | ID: ppmedrxiv-21253946

Résumé

Mutations at both the receptor-binding domain (RBD) and the amino (N)-terminal domain (NTD) of the SARS-CoV-2 Spike (S) glycoprotein can alter its antigenicity and promote immune escape. We identified that SARS-CoV-2 lineages circulating in Brazil with mutations of concern in the RBD independently acquired convergent deletions and insertions in the NTD of the S protein, which altered the NTD antigenic-supersite and other predicted epitopes at this region. These findings support that the ongoing widespread transmission of SARS-CoV-2 in Brazil is generating new viral lineages that might be more resistant to neutralization than parental variants of concern.

4.
SSRN; 2020.
Preprint | SSRN | ID: ppcovidwho-1538

Résumé

Following the outbreak of the COVID-19 pandemic, the Federal Reserve led a coordinated mix of unconventional monetary policies with Central Banks around the wor

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