Early Estimates of Bivalent mRNA Vaccine Effectiveness in Preventing COVID-19–Associated Hospitalization Among Immunocompetent Adults Aged ≥65 Years — IVY Network, 18 States, September 8–November 30, 2022

Abstract

this report was posted as an MMWR Early Release on the MMWR website (https://www.cdc.gov/mmwr).Monovalent COVID-19 mRNA vaccines, designed against the ancestral strain of SARS-CoV-2, successfully reduced COVID-19related morbidity and mortality in the United States and globally (1,2). However, vaccine effectiveness (VE) against COVID-19associated hospitalization has declined over time, likely related to a combination of factors, including waning immunity and, with the emergence of the Omicron variant and its sublineages, immune evasion (3). To address these factors, on September 1, 2022, the Advisory Committee on Immunization Practices recommended a bivalent COVID-19 mRNA booster (bivalent booster) dose, developed against the spike protein from ancestral SARS-CoV-2 and Omicron BA.4/BA.5 sublineages, for persons who had completed at least a primary COVID-19 vaccination series (with or without monovalent booster doses) ≥2 months earlier (4). Data on the effectiveness of a bivalent booster dose against COVID-19 hospitalization in the United States are lacking, including among older adults, who are at highest risk for severe COVID-19-associated illness. During September 8-November 30, 2022, the Investigating Respiratory Viruses in the Acutely Ill (IVY) Network § assessed

Early Estimates of Bivalent mRNA Vaccine Effectiveness in Preventing COVID-19–Associated Emergency Department or Urgent Care Encounters and Hospitalizations Among Immunocompetent Adults — VISION Network, Nine States, September–November 2022

“…Additional studies are needed to evaluate VE against outcomes such as COVID-19–associated severe respiratory illness or death. The IVY Network, an adult inpatient VE network, recently found higher estimated VE in adults aged ≥65 years compared with estimates for those aged ≥18 years included in this analysis ( 6 ). This might reflect differences in population subgroups evaluated.…”

Bivalent mRNA vaccine improves antibody-mediated neutralization of many SARS-CoV-2 Omicron lineage variants

“…Two recent CDC-led vaccine effectiveness (VE) studies found that the bivalent mRNA vaccine booster provided 42-73% additional protection against COVID-19-associated hospitalization compared with 2 to 4 monovalent COVID-19 vaccine doses during September-November 2022 15, 16 , when BA.5 and BQ.1/BQ.1.1 predominated. In the present study, from the post-third dose monovalent sera to post-fourth dose bivalent vaccine sera, the neutralizing titers increased by 7.1-fold against BA.5 and 12-fold against BQ.1 and BQ.1.1 (Fig.…”

Laboratory-Confirmed COVID-19 Case Incidence Rates Among Residents in Nursing Homes by Up-to-Date Vaccination Status — United States, October 10, 2022–January 8, 2023

“…Another recent study found that bivalent booster doses produced a robust immunologic response in nursing home residents ( 6 ). Bivalent booster doses have also been shown to provide additional protection against severe outcomes associated with COVID-19, compared with monovalent vaccination alone, including protection against COVID-19–associated emergency department and urgent care visits among adults aged ≥18 years and protection against COVID-19 hospitalization among adults aged ≥65 years ( 7 , 8 ). Public health efforts to sustain up-to-date COVID-19 vaccination status among nursing home residents (including recommended vaccinations and booster doses) are critical to protecting this population.…”