P-2069. Updated 2023–2024 (Monovalent XBB.1.5) COVID-19 Vaccine Effectiveness Against COVID-19–associated Hospitalization Among Adults — IVY Network, 20 U.S. States

Data from the Investigating Respiratory Viruses in the Acutely Ill (IVY) Network were used to conduct a case-control analysis estimating updated 2023–2024 COVID-19 vaccine effectiveness (VE) against COVID-19–associated hospitalization. During September 21, 2023–March 31, 2024, adults aged ≥18 years with COVID-19-like illness were enrolled at 26 hospitals in 20 U.S. states. COVID-19 case patients tested positive for SARS-CoV-2 by a nucleic acid or antigen test within 10 days of illness onset, while control patients tested negative for SARS-CoV-2. VE was estimated using multivariable logistic regression comparing the odds of receipt of an updated 2023–2024 COVID-19 vaccine dose versus no updated dose among case and control patients. VE models were adjusted for age, sex, race and ethnicity, admission date, and geographic region. Results were stratified by age, Charlson Comorbidity Index (CCI) score, and immunocompromised status.

A total of 7843 adults were enrolled, including 2090 COVID-19 case patients and 5753 control patients. Among immunocompetent adults, VE against COVID-19–associated hospitalization was 41% (95% CI=28%–51%, median time since updated dose = 73 days) among persons aged ≥18 years, 48% (95% CI=19%–66%) among persons aged 18–64 years, 42% (95% CI=27%–53%) among persons aged ≥65 years, 42% (95% CI=22%–57%) among persons with CCI < 5, and 41% (95% CI=23%–54%) among persons with CCI ≥5 (Figure). Among immunocompromised adults, VE against COVID-19–associated hospitalization was 25% (95% CI=0%–44%, median time since updated dose = 74 days).

Updated 2023–2024 COVID-19 vaccination provided protection against COVID-19–associated hospitalization among immunocompetent adults. VE was similar across age groups and CCI scores, but may be lower among immunocompromised adults.

Adam S. Lauring, MD, PhD, Roche: Advisor/Consultant Ithan Peltan, MD, Bluejay Diagnostics: Grant/Research Support|Regeneron: Grant/Research Support Nicholas Mohr, MD, Endpoint Health: Grant/Research Support Steven Chang, MD, PhD, Kiniksa: Consulting fee Christopher Mallow, MD, Medical Legal Consulting: Advisor/Consultant Ivana Vaughn, PhD, eMax Health Systems, LLC: Grant/Research Support|Evidera, Inc: Grant/Research Support