Waning of bivalent mRNA vaccine effectiveness against COVID-19-associated hospitalization among immunocompetent adults aged ≥ 18 years—IVY Network, 20 U.S. States, September 8, 2022–April 1, 2023
Presenter: Jennifer DeCuir, MD, PhD, Surveillance and Prevention Branch, Coronavirus and Other Respiratory Viruses Division, U.S. Centers for Disease Control and Prevention, Atlanta, GA.
Among immunocompetent adults age 18 and older, the effectiveness of bivalent mRNA vaccination largely waned by 6 months in an IVY (Investigating Respiratory Viruses in the Acutely Ill) analysis spanning September 8, 2022 through May 31, 2023, presented in an oral session at ID Week 2023. Less evidence of bivalent vaccine effectiveness waning, however, was found among immunocompromised adults, stated Jennifer DeCuir, MD, PhD, Surveillance and Prevention Branch, Coronavirus and Other Respiratory Viruses Division, the Centers for Disease Control and Prevention (CDC), Atlanta, GA.
In September 2022, the CDC Advisory Committee on Immunization Practices recommended a bivalent mRNA COVID-19 booster for persons who had completed at least a primary COVID-19 vaccination series 2 or months earlier. While early data showed high effectiveness for such a booster in preventing COVID-19-associated hospitalization within 45 days among adults, little is known about the protection’s durability, Decuir said.
Investigators conducted a case-control analysis measuring bivalent vaccine effectiveness against COVID-19–associated hospitalization, enrolling a total of 6,134 immunocompetent adults age 18 and older with COVID-19-like illness in the IVY Network. Those testing positive for SARS-CoV-2 by a nucleic acid or antigen test within 10 days of illness onset were designated as COVID-19 case patients (N = 2,483), and those testing negative were designated as controls (N = 3,651).
Absolute and relative bivalent vaccine effectiveness, adjusted for age, sex, race, and ethnicity, admission date, and U.S. Health and Human Services region, were measured by multivariable logistic regression. For assessing absolute and relative vaccine effectiveness, respectively, researchers used unvaccinated patients and patients who received 2 to 4 doses of monovalent-only mRNA vaccine as a reference group. Bivalent vaccine effectiveness was calculated for 2 periods, from 7 to 89 days and from 90 to 179 days following receipt of the booster dose to onset of illness.
In the entire age group of immunocompetent adults, the adjusted vaccine effectiveness against COVID-19-associated hospitalization was:
- 51% for bivalent doses at 7 to 89 days
- 12% for bivalent doses at 90 to 179 days
- 10% for monovalent doses only, the last dose given a median of 395 days earlier.
Among immunocompetent adults age 65 and older, the adjusted vaccine effectiveness was:
- 53% for bivalent booster doses at 7 to 89 days
- 10% for bivalent booster doses at 90 to 179 days
- 1% for monovalent doses only, at a median of 385 days.
Among younger immunocompetent patients (18–64 years), the adjusted vaccine effectiveness was:
- 43% for bivalent booster doses at 7 to 89 days
- 17% for bivalent booster doses at 90 to 179 days
- 20% for monovalent doses only, at a median of 412 days.
Among immunocompromised adults, the adjusted vaccine effectiveness was:
- 55% for bivalent booster doses 7 at 89 days
- 43% for bivalent booster doses at 90 at 179 days
- 13% for monovalent doses only, at a median of 374 days.
Greater use of masking, social distancing, and outpatient COVID-19 antiviral treatment might explain why vaccine effectiveness wane less among immunocompromised patients, DeCuir speculated.
Noting the moderate vaccine effectiveness for protecting against COVID-19-associated hospitalization at less than 90 days from bivalent mRNA vaccination, and the waning effectiveness from 90 to 179 days after vaccination, DeCuir suggested that an additional booster dose could improve protection against COVID-19-associated hospitalization among older adults. She concluded, “Overall, these results support current US recommendations for all eligible adults to receive an updated COVID-19 vaccine dose during the 2023–2024 respiratory virus season.”
Disclosures. The IVY network currently consists of 25 medical centers in 20 US states. IVY was created initially in 2019 to evaluate how well influenza vaccines work to prevent severe flu illness among intensive care unit patients, but has since been expanded to include experience with COVID-19 and respiratory syncytial virus infection.
Dr. DeCuir had no disclosures.