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The emergence of the new Brazilian variant of concern, P.1 lineage (Gamma), raised concern about its impact on the epidemiological profile of COVID-19 cases due to its higher transmissibility rate and immune evasion ability. Using 272 whole-genome sequences combined with epidemiological data, we showed that P.1 introduction in São José do Rio Preto, São Paulo, Brazil, was followed by the displacement of eight circulating SARS-CoV-2 variants and a rapid increase in prevalence two months after its first detection. Our findings support that the P.1 variant is associated with an increase in mortality risk and severity of COVID-19 cases in younger aged groups, which corresponds to the unvaccinated population at the time. Moreover, our data highlight the beneficial effects of vaccination indicated by a pronounced reduction of severe cases and deaths in immunized individuals, reinforcing the need for rapid and massive vaccination.

IntroductionIn a global context, COVID-19 is the most significant health threat in the present days, evidenced by the fact that, in just over four months, SARS-CoV-2 has spread to 171 countries, reaching a Pandemic status. Most patients with COVID-19 have a mild course of the disease. However, approximately 20% develop severe illness with a high mortality rate which is associated with age, comorbidities, and immunosuppression. Epidemiological studies are used to reveal the extent of viral spread in homes, communities, and hospitals. Thus, preventive and control measures can be established by the authorities.ObjectiveIn this study, patients with suspect COVID-19 symptoms who search for hospital care at the city of Sao José do Rio Preto (Sao Paulo, Brazil) were monitored, in order to identify the first case of this new disease in the region. In the first two months (March and April), more than 3000 individuals looked for the public and private health system with suspected respiratory symptoms, but only 164 (8.4%) were COVID-19 confirmed.ResultsFrom those, males (56.1%) and patients of the age distribution of 16-59 (91.2%), with diarrhea (22.2%), runny nose (25%), altered taste (15.9%), and anosmia (11.6%) presented statistical significance, although none comorbidities were related with COVID-19 occurrence. The odds ratio analysis supports this finding. Days of onset of symptoms are positively associated with whit viral load, and the same happens with the occurrence of symptoms (dyspnea and low saturation).