The longer it has been since an individual’s last dose of the original (monovalent) COVID-19 vaccines, the greater the relative benefits of receiving the recently approved, bivalent boosters, a real-world study has found.
In addition, the newer booster vaccines provide significant additional protection against infection in seniors when compared to the original vaccines alone, according to investigators with the Centers for Disease Control and Prevention.
These findings are the first published estimates of efficacy for the newly authorized bivalent mRNA booster vaccines, the authors reported in a study published Nov. 22.
Protection increases for seniors
Investigators sought to find whether people who received the newer bivalent vaccines derived more protection against symptomatic COVID-19 than those who received the monovalent vaccines alone. They also compared effectiveness of the bivalent vaccine at different time intervals since the recipients’ last shots with the original vaccines. Data came from COVID-19 testing at pharmacies nationwide between September 14 and November 11 2022. All participants were immunocompetent.
In older as well as younger age groups, investigators found a relative increase in effectiveness. For those aged 65 years and older, the effectiveness of a newer, bivalent booster dose compared to monovalent boosters rose from 23% at two to three months after the recipient’s most recent monovalent dose to 43% at eight months after the most recent monovalent dose.
For those aged 50 to 64 years, protection derived from the bivalent booster dose compared to monovalent vaccines rose from 31% at two to three months after receipt of the most recent monovalent dose to 48% at eight months.
The relative increase in protection from the bivalent vaccines is likely due to the waning of the monovalent vaccines’ effectiveness over time, wrote Tamara Pilishvili, PhD, of the CDC’s National Center for Immunization and Respiratory Diseases.
“All persons should stay up-to-date with recommended COVID-19 vaccines, including bivalent booster doses, if it has been two or more months since their last monovalent vaccine dose,” she and her colleagues concluded.
The updated, bivalent vaccine is currently the preferred booster.
Double-duty vaccine
The original vaccines were developed to fight COVID-19 were monovalent, meaning that they worked against the single, original strain of the SARS-CoV-2 virus. Drugmakers Pfizer-BioNTech and Moderna later introduced bivalent vaccines, which create antibodies against two different types of the virus — the original strain and an omicron strain.
The CDC study was published in the agency’s Morbidity and Mortality Weekly Report.
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