CDC studies on vaccine effectiveness of bivalent COVID-19 vaccine amongst vaccinated vs. unvaccinated adults aged ≥65 years in 2022-23


In a current Morbidity and Mortality Weekly Report (MMWR), the US Facilities for Illness Management and Prevention (CDC) reported how coronavirus illness 2019 (COVID-19) mortality charges various amongst unvaccinated and vaccinated adults aged ≥65 years in the US between 2022 and 2023.

Study: Notes from the Field: Comparison of COVID-19 Mortality Rates Among Adults Aged ≥65 Years Who Were Unvaccinated and Those Who Received a Bivalent Booster Dose Within the Preceding 6 Months — 20 U.S. Jurisdictions, September 18, 2022–April 1, 2023. Image Credit: GroundPicture/Shutterstock.comResearch: Notes from the Subject: Comparability of COVID-19 Mortality Charges Amongst Adults Aged ≥65 Years Who Had been Unvaccinated and These Who Acquired a Bivalent Booster Dose Throughout the Previous 6 Months — 20 U.S. Jurisdictions, September 18, 2022–April 1, 2023. Picture Credit score: GroundPicture/


The CDC really helpful bivalent COVID-19 vaccines for the primary time on September 1, 2022, for the aged inhabitants of the U.S.

Following these vaccine packages, research analyzed COVID-19 circumstances and mortality charges by vaccination standing quickly after authorization of bivalent COVID-19 vaccines, which confirmed these vaccines conferred extra safety.

In regards to the report

This follow-up CDC report compiled information on the impact and sturdiness of bivalent COVID-19 booster vaccine amongst adults aged ≥65 years. Particularly, they estimated mortality price ratios (RRs) in vaccinated folks by time since bivalent vaccination throughout extreme acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant’s predominance durations. 

Omicron BA.5 dominated the interval between September 18 and November 5, 2022; likewise, Omicron BQ.1/BQ.1.1 and XBB.1.5 dominated between November 6, 2022, and January 21, 2023, and January 22 and April 1, 2023, respectively. The staff additionally estimated RRs for unvaccinated controls.

The CDC retrieved research information, i.e., weekly counts of COVID-19–associated deaths amongst unvaccinated people and bivalent booster recipients for September 18, 2022–April 1, 2023, from 20 U.S. jurisdictions. Observe that the COVID-19 case surveillance information within the U.S. is linked to immunization registries and registration databases on a routine foundation.

The CDC estimated common weekly mortality charges based mostly on the date of pattern assortment throughout every interval evaluated on this research stratified by vaccination standing and time lapsed since receiving the bivalent vaccine’s booster dose, i.e., six months. 

They categorized charges for unvaccinated people by charges amongst bivalent booster dose recipients after detrending the linear variations in weekly mortality charges. They estimated the remaining 95% confidence intervals (CIs) from the variation in RRs noticed. They carried out all analyses per CDC coverage and federal legislation.


Amongst these≥65 years who obtained a bivalent COVID-19 vaccine booster or remained unvaccinated, there have been 8,161 COVID-19–associated deaths throughout 20 U.S. jurisdictions between September 18, 2022, and April 1, 2023. 

The proportion of COVID-19-related deaths in 80-year-olds was 58% however inconsistent amongst vaccinated and unvaccinated people and throughout the three Omicron predominance durations. 

Nonetheless, mortality charges amongst unvaccinated people throughout all three durations had been excessive. Quite the opposite, mortality charges amongst adults aged ≥65 peaked throughout the BQ.1/BQ.1.1 dominance interval, i.e., December 2022. 

The CDC additionally reported time-stratified mortality charges amongst unvaccinated and vaccinated folks two weeks to 2 months after receiving a bivalent booster vaccination.

They discovered that mortality RRs markedly diminished between the BA.5- and XBB.1.5-predominant interval from 16.3 to eight.4, representing a average decline in vaccine effectiveness (VE) from 94% to 88%.

Then again, mortality RRs had been comparable in individuals who obtained a bivalent vaccination two weeks to 2 months earlier or between three and 6 months earlier than the BQ.1/BQ.1.1- the XBB.1.5-predominant durations, with RRs of 11.4 and 11.0 and eight.4 and seven.3, respectively.


To summarize, a bivalent COVID-19 booster vaccination supplied substantial and sturdy safety towards COVID-19–associated dying in adults aged ≥65 years.

Extra importantly, there was no corroboration of waning as much as six months post-vaccination, much like different research evaluating VE towards extreme illness and dying. Thus, CDC strongly recommends that each one folks aged ≥6 months stay updated with up to date COVID-19 vaccines, together with a number of extra bivalent dose(s).

Further vaccine doses are elective for immunocompromised and other people aged ≥65 years.

The SARS-CoV-2 spike protein within the bivalent vaccine is completely different; thus, CDC reported a slight lower of 6% in immune evasion throughout the Omicron XBB.1.5 interval in comparison with the Omicron BA.5 interval.

Nonetheless, the research information are clinically related, particularly relating to COVID-19 vaccine composition. Within the U.S., the COVID-19 public well being emergency ended on Could 11, 2023.

So, they discontinued routine monitoring of COVID-19 incidence, hospitalization, and dying charges stratified by vaccine standing. But, CDC continues to observe VE by way of well-controlled research (e.g., the IVY networks).