Clinical and Virological Features of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Variants in Vaccinated and Unvaccinated Patients in Mexico City (preprint)

ABSTRACT

Background: Coronavirus disease 2019 (COVID-19) vaccines are very effective at protecting against severe disease and death. However, the impact of the vaccine used, viral variants, and host factors on disease severity in vaccinated individuals remain poorly understood. Here we compared COVID-19 clinical presentations and outcomes in vaccinated and unvaccinated patients in a tertiary hospital in Mexico City. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants were also determined to study their potential impact on disease severity. Methods: From March to September 2021, clinical and demographic characteristics were obtained from 1,014 individuals with a documented SARS-CoV-2 infection, and viral variants were identified in a subset of 386 patients. We compared three groups of patients 1) unvaccinated, 2) partially vaccinated, and 3) fully vaccinated, stratifying by age groups (<30 years, 31-60 years, and > 61 years) on the clinical outcomes, and including in-hospital mortality. We fitted different multivariate statistical models to evaluate the impact of vaccination status, SARS-CoV-2 lineages, vaccine types, and clinical parameters. Results: 1,014 patients were included, with 11% being outpatients and 88% hospitalized. Most hospitalized patients were unvaccinated. In patients over 61 years old, mortality was significantly higher in unvaccinated compared to fully vaccinated individuals. In patients aged 31 to 60 years, vaccinated patients were more likely to be outpatients (46%) than unvaccinated individuals (6.1%). The percentage of critical patients over 61 years was higher in unvaccinated than vaccinated individuals (75% vs. 56%, p < 0.001). We found immune disease (OR 3.12, 95% CI 1.09-8.34, p = 0.02) and age above 61 years old (OR 3.51, 95% CI 2.3-5.2, p = 5.9e-10) as risk factors. While fully vaccination was found as the most protective factor against in-hospital death (OR 0.25, 95% CI 0.12-0.46, p = 2.89e-05). Conclusions: This study suggests that vaccination and particularly full vaccination is essential to reduce mortality in a comorbid population such as that of Mexico. When analyzing the presence of comorbidities and advanced ages as risk factors, complete vaccination was the most significant protective factor against death by COVID-19. We found no strong association between SARS-CoV-2 lineages or vaccine type and disease severity.