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

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.

Comprehensive evaluation of the impact of sociodemographic inequalities on adverse outcomes and excess mortality during the COVID-19 pandemic in Mexico City (preprint)

The impact of the COVID-19 pandemic in Mexico City has been sharp, as several social inequalities coexist with chronic comorbidities. Here, we conducted an in-depth evaluation of the impact of social, municipal, and individual factors on the COVID-19 pandemic in working-age population living in Mexico City. To this end, we used data from the National Epidemiological Surveillance System; furthermore, we used a multidimensional metric, the social lag index (DISLI), to evaluate its interaction with mean urban population density (MUPD) and its impact on COVID-19 rates. Influence DISLI and MUPD on the effect of vehicular mobility policies on COVID-19 rates were also tested. Finally, we assessed the influence of MUPD and DISLI on discrepancies of COVID-19 and non-COVID-19 excess mortality compared with death certificates from the General Civil Registry. We detected vulnerable groups who belonged to economically active sectors and who experienced increased risk of adverse COVID-19 outcomes. The impact of social inequalities transcends individuals and has significant effects at a municipality level, with and interaction between DISLI and MUPD. Marginalized municipalities with high population density experienced an accentuated risk for adverse COVID-19 outcomes. Additionally, policies to reduce vehicular mobility had differential impacts across marginalized municipalities. Finally, we report an under-registry of COVID-19 deaths and significant excess mortality associated with non-COVID-19 deaths closely related to MUPD/DISLI in an ambulatory setting, which could be a negative externality of hospital reconversion. In conclusion, social, individual, and municipality-wide factors played a significant role in shaping the course of the COVID-19 pandemic in Mexico City.