Comparison of the Clinical and Laboratory Findings and Outcomes of Hospitalized COVID-19 Patients who Were Vaccinated with Coronavac or Unvaccinated: An Analytical, Cross Sectional Study

PurposeCOVID-19 vaccines have been shown to be highly effective; however, vaccine breakthrough infections resulting from hospitalization may still occur in a small percentage of vaccinated individuals. We investigated whether the clinical and microbiological features and outcomes were different between hospitalized COVID-19 vaccinated and unvaccinated COVID-19 patients.MethodsThis multicentre, prospective, cross-sectional study was performed between April and June 2021. All hospitalized COVID-19 patients who previously had at least one dose of Coronavac were included in the study, along with some unvaccinated patients. All epidemiologic, clinical and laboratory data of the patients were recorded and compared between the vaccinated and unvaccinated individuals.ResultsThere were 69 fully Coronavac vaccinated and 175 unvaccinated patients. All breakthrough infections occurred in the first 3 months of vaccination. Fully vaccinated patients were older and had more comorbidities than unvaccinated patients (p<0.05). There were minor differences between the groups in the symptoms, physical and laboratory findings, anti-spike IgG positivity rate, mean anti-SARS-CoV-2 S antibody level, and severity of COVID-19. The mortality rate of fully vaccinated patients was higher than the mortality rate in unvaccinated patients; however, vaccination was not an independent risk factor for mortality.ConclusionsHospitalized patients with breakthrough COVID-19 after Coronavac vaccination were usually older with comorbidities. The severity and clinical outcomes of these cases were similar to those of unvaccinated patients. Our findings suggest that the immune response elicited by Coronovac could be insufficient to prevent COVID-19-related severe disease and death within 3 months of vaccination among elderly people with comorbidities.