Updated Bivalent COVID-19 Vaccines Reduce Risk of Hospitalization and Severe Outcomes in Adults: An Observational Cohort Study

Nicholas Mielke; Steven Johnson; Charlotte O'Sullivan; Mohammad Usama Toseef; Amit Bahl

doi:10.14740/jocmr5145

Updated Bivalent COVID-19 Vaccines Reduce Risk of Hospitalization and Severe Outcomes in Adults: An Observational Cohort Study

J Clin Med Res. 2024 May;16(5):208-219. doi: 10.14740/jocmr5145. Epub 2024 May 29.

Authors

Nicholas Mielke^{1

2}, Steven Johnson³, Charlotte O'Sullivan¹, Mohammad Usama Toseef⁴, Amit Bahl⁵

Affiliations

¹ Oakland University William Beaumont School of Medicine, Rochester, MI, USA.
² Department of Medicine, Creighton University School of Medicine, Omaha, NE, USA.
³ Department of Anesthesia, Keck Medicine of University of Southern California, Los Angeles, CA, USA.
⁴ Corewell Health Research Institute, Royal Oak, MI, USA.
⁵ Department of Emergency Medicine, Corewell Health William Beaumont University Hospital, Royal Oak, MI, USA.

Abstract

Background: This study evaluates the real-world effectiveness of updated bivalent coronavirus disease 2019 (COVID-19) vaccines in adults, as the virus evolves and the need for new vaccinations increases.

Methods: In this observational, retrospective, multi-center, cohort analysis, we examined emergency care encounters with COVID-19 in metro Detroit, Michigan, from January 1, 2022, to March 9, 2023. Patients were categorized by vaccination status: unvaccinated, fully vaccinated, fully vaccinated and boosted (FV&B), or fully vaccinated and bivalent boosted (FV&BB). The primary outcome was to assess the impact of bivalent COVID-19 vaccinations on the risk of composite severe outcomes (intensive care unit (ICU) admission, mechanical ventilation, or death) among patients presenting to a hospital with a primary diagnosis of COVID-19.

Results: A total of 21,439 encounters met inclusion criteria: 9,630 (44.9%) unvaccinated, 9,223 (43.0%) vaccinated, 2,180 (10.2%) FV&B, and 406 (1.9%) FV&BB. The average age was 48.8, with 59.6% female; 61.1% were White, 32.8% Black, and 6.0% other races. Severe disease affected 5.5% overall: 5.0% unvaccinated, 5.7% vaccinated, 7.0% FV&B, and 4.7% FV&BB (P = 0.001). Severe disease rates among admitted patients were 13.3% unvaccinated, 11.9% vaccinated, 12.2% boosted, and 8.1% FV&BB (P = 0.052). The FV&BB group showed a 4.0% (P = 0.0369) lower risk of severe disease compared to FV&B and a 5.1% (P = 0.0203) lower probability of hospitalization.

Conclusions: As the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to mutate and evolve, updated vaccines are necessary to better combat COVID-19. In a real-world hospital-based population, this investigation demonstrates the incremental benefit of the bivalent booster vaccine in reducing the risk of hospitalization and severe outcomes in those diagnosed with COVID-19 compared to all other forms of vaccination.

Keywords: Booster dose; COVID-19; Death; Hospitalization; Mortality; SARS-CoV-2; Severe illness; Vaccination.

Grants and funding

None to declare.