Bivalent COVID-19 Boosters Restored Protection Against Death, Especially for Older Adults

Protection from the original COVID-19 vaccines faded as immunity waned and new Omicron sublineages spread. On September 1, 2022, CDC recommended an updated bivalent booster, with an added Omicron BA.4/BA.5 component, for people aged 12 and older (later extended to 6 months and up). Data from 24 jurisdictions linking case reports, vaccination registries and death records showed what it did: it restored protection against death, most of all for older adults.

COVID-19 Incidence and Mortality Among Unvaccinated and Vaccinated Persons Aged ≥12 Years: CDC's video summary of the report.

The data

From October 3, 2021, to December 24, 2022, these jurisdictions reported 21,296,326 COVID-19 cases and 115,078 deaths among people aged 12 and older. Researchers compared rates in unvaccinated people with rates in vaccinated people across the Delta and Omicron (BA.1, BA.2, early and late BA.4/BA.5) periods, as rate ratios: how many times higher the unvaccinated rate was.

Late BA.4/BA.5 period

Monovalent-only recipients also died at 2.6 times the rate of bivalent recipients. The gap was largest among older adults:

Waning — and restoring

Protection from monovalent boosters faded over time and across variants. Comparing unvaccinated people with those boosted 2 weeks to 2 months earlier, the mortality rate ratio fell from 50.7 in the Delta period to 7.4 in the early BA.4/BA.5 period; and during that early BA.4/BA.5 period it fell further with time since the booster — 4.6 at 6–8 months, 4.5 at 9–11 months, 2.5 at 12 months or more. A bivalent booster in the previous 2 weeks to 2 months brought it back to 15.2 in the late BA.4/BA.5 period. Protection against infection after a recent bivalent booster was similar to a recent monovalent one, with signs of waning after 3 months.

Uptake was low: only 17.5 percent of people aged 12 and older had received a bivalent booster.

Limits

Monovalent and bivalent boosters were authorized at different times, so their recipients had different times since vaccination. Additional primary doses for immunocompromised people could not be separated from boosters. The study could not adjust for differences in prior infection, health conditions, or testing and prevention behavior; home testing affected case counts; national variant estimates were applied everywhere; boosters could be misclassified; and the jurisdictions cover about half the U.S. population.

The recommendation, then

The report concluded that everyone should stay up to date with COVID-19 vaccination, with eligible people receiving one bivalent booster at least 2 months after their primary series or last monovalent booster.

Sources

Based on "COVID-19 Incidence and Mortality Among Unvaccinated and Vaccinated Persons Aged ≥12 Years by Receipt of Bivalent Booster Doses and Time Since Vaccination — 24 U.S. Jurisdictions, October 3, 2021–December 24, 2022," Morbidity and Mortality Weekly Report, Centers for Disease Control and Prevention; a work of the United States government in the public domain.

• The film is the agency's own low-resolution copy, recovered from the Internet Archive's record of cdc.gov.