The Third Wave: Comparing Seasonal Trends in COVID-19 Patient Data at a Large Hospital System in New York City

The third wave of COVID-19 is unique in that vaccines have been widely available; however, the highly transmissible Delta variant has been the predominant strain. Temporal changes of hospitalized patient characteristics should continue to be analyzed as COVID-19 progresses. OBJECTIVES: Compare the demographics and outcomes of hospitalized patients during New York City’s third wave of COVID-19 to the first two waves. DESIGN, SETTING, AND PARTICIPANTS: Retrospective cohort study across five hospitals within Mount Sinai Health System, a quaternary academic medical system in New York City. Participants were adult inpatients admitted with COVID-19 identified by positive severe acute respiratory syndrome coronavirus 2 polymerase chain reaction at admission or clinical documentation of infection during the three waves of COVID-19. MAIN OUTCOMES AND MEASURES: Patient demographics, comorbidities, vaccination status, and outcomes of COVID-19 patients hospitalized at Mount Sinai Health System were examined. Patients admitted during the third wave were notably younger than the first two, were mostly unvaccinated against COVID-19, and there was a higher rate of patients who self-report as Black or African American as compared with the first two waves. The rate of patients requiring ICU level of care remained consistent throughout all three periods; however, the rate of patients requiring invasive mechanical ventilation decreased and inhospital mortality has trended down. Unvaccinated patients in the third wave are significantly younger with lower comorbidity burden than fully vaccinated patients. RESULTS: A total of 13,036 patients were included between the 3 waves. In the 3rd wave patients were notably younger, with a lower intubation rate and lower inhospital death rate. In the 3rd wave, 400 (62.9%) were unvaccinated, 236 (37.1%) were fully vaccinated, and 34 (4.8%) were partially vaccinated. Unvaccinated patients had similar rates of intubation and invasive mechanical ventilation compared with vaccinated patients, though inhospital mortality was lower in unvaccinated patients compared with vaccinated patients which may be expected given their lower age and burden of comorbidities. CONCLUSIONS AND RELEVANCE: We continue to see improved outcomes in hospitalized COVID-19 patients. Patients that are unvaccinated against COVID-19 are younger and have less reported comorbidities.