The main coronavirus disease 2019 (COVID‐19) vaccine formulations used today are mainly based on the wild‐type severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) spike glycoprotein as an antigen. However, new virus variants capable of escaping neutralization activity of serum antibodies elicited in vaccinated individuals have emerged. The Omicron (B.1.1.529) variant caused epidemics in regions of the world in which most of the population has been vaccinated. In this study, we aimed to understand what determines individual's susceptibility to Omicron in a scenario of extensive vaccination. For that purpose, we collected nasopharynx swab (n = 286) and blood samples (n = 239) from flu‐like symptomatic patients, as well as their vaccination history against COVID‐19. We computed the data regarding vaccine history, COVID‐19 diagnosis, COVID‐19 serology, and viral genome sequencing to evaluate their impact on the number of infections. As main results, we showed that vaccination in general did not reduce the number of individuals infected by Omicron, even with an increased immune response found among vaccinated, noninfected individuals. Nonetheless, we found that individuals who received the third vaccine dose showed significantly reduced susceptibility to Omicron infections. A relevant evidence that support this finding was the higher virus neutralization capacity of serum samples of most patients who received the third vaccine dose. In summary, this study shows that boosting immune responses after a third vaccine dose reduces susceptibility to COVID‐19 caused by the Omicron variant. Results presented in this study are useful for future formulations of COVID‐19 vaccination policies.

COVID-19 continues to spread around the world despite significant progress in vaccine distribution and population immunity. The dynamics of the antiviral antibody response postvaccination is critical to evaluate vaccine effectiveness across different vaccine platforms and over time.

Background Phylogenetic studies indicate bats as original hosts of SARS-CoV-2. However, it remains unclear whether other animals, including pets, are crucial in the spread and maintenance of COVID-19 worldwide. Methods In this study, we analyzed the first fatal case of a SARS-CoV-2 and FeLV co-infection in an eight-year-old male cat. We carried out a clinical evaluation and several laboratory analyses. Results As main results, we observed an animal presenting severe acute respiratory syndrome and lesions in several organs, which led to the animal’s death. RT-qPCR analysis showed a SARS-CoV-2 as the causative agent. The virus was detected in several organs, indicating a multisystemic infection. The virus was found in a high load in the trachea, suggesting that the animal may have contribute to the transmission of the virus. The whole-genome sequencing revealed an infection by SARS-CoV-2 Gamma VOC (P.1), and any mutations indicating host adaptation were observed. Conclusion Our data show that FeLV-positive cats are susceptible to SARS-CoV-2 infection and raise questions about the potential of immunocompromised FeLV-positive cats to act as a reservoir for SARS-CoV-2 new variants.

Background: The correct understanding of the epidemiological dynamics of COVID-19, caused by the SARS-CoV-2, is essential for formulating public policies of disease containment. Methods: In this study, we constructed a picture of the epidemiological dynamics of COVID-19 in a Brazilian population of almost 17000 patients in 15 months. We specifically studied the fluctuations of COVID-19 cases and deaths due to COVID-19 over time according to host gender, age, viral load, and genetic variants. Results: As the main results, we observed that the numbers of COVID-19 cases and deaths due to COVID-19 fluctuated over time and that men were the most affected by deaths, as well as those of 60 or more years old. We also observed that individuals between 30- and 44-years old were the most affected by COVID-19 cases. In addition, the viral loads in the patients’ nasopharynx were higher in the early symptomatic period. We found that early pandemic SARS-CoV-2 lineages were replaced by the variant of concern (VOC) P.1 (Gamma) in the second half of the study period, which led to a significant increase in the number of deaths. Conclusions: The results presented in this study are helpful for future formulations of efficient public policies of COVID-19 containment.

Developing of the manuscript, production of the results and graphics and interpretation of data; RSN: constructions of the ideas, elaboration of manuscript and support in the analysis of the relationships between climatic variables and dengue incidence; PSB: contribution in the interpretation and showing of the structure of methodology; JPF: contributions to analyze epidemiological characteristics and constructions of the ideas; JHA: contributions to analyze, review and constructions of the ideas; EBM: contributions to analyzing relationships between dengue and climatic variables; ECM: contributions with discussions of ideas and review; WBL: contributions with the review of the manuscript.