November 22 – Updated for reinforcement covidCOVID-19 offers greater protection against the new variant in people who have previously received up to four doses of the older vaccine, a real-world study conducted in the United States showed.
The study of more than 360,000 people, published in Morbidity and Mortality Weekly Report, offers the first evidence that the new vaccines from Pfizer-BioNTech and Moderna provide better protection than the original injection.
Since its introduction in September, booster vaccines, containing both the parent strain and the Omicron BA.4/5 strain, have provided greater benefit to young adults aged 18-49.
Compared to the original vaccines, the relative efficacy of the new boosters was 56% in people aged 18 to 49 years, compared with 48% in those aged 50 years, when given eight months or longer, according to the study. among those 65 years or older.
The variation in efficacy was smaller, in the order of 28 to 31%, when boosters were administered at 2 to 3 month intervals.
The study authors cautioned that participants may not remember their vaccination status, past infection history, and underlying medical conditions, and that the low number of bivalent boosters could skew the results.
Over the past two months, the BQ.1 and BQ.1.1 subvariants have become the dominant coronavirus strains in the United States, overtaking the Omicron BA.5 subvariant, based on which the vaccines were updated.