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Drop in COVID Vaccine Effectiveness Suggests Need for Boosters

The effectiveness of the two most common COVID-19 vaccines declined over time in an older group of patients, suggesting that booster doses may be needed to protect recipients over the long term, according to a new study.

Also seen in that group of US veterans, who had a median age of 67 years: Those receiving "the Moderna vaccine consistently had higher antibody levels, compared with recipients of the Pfizer-BioNTech vaccine, across age groups and time since vaccination," said Kristina L. Bajema, MD, of the CDC's COVID-19 Response Team, and associates.

Effectiveness of the Moderna vaccine was 89.6% at 14-119 days after patients had received the second dose, compared with 86.0% for the Pfizer vaccine. After 120 or more days, vaccine effectiveness had dropped to 86.1% for Moderna and 75.1% for Pfizer, the investigators reported in the Morbidity and Mortality Weekly Report.

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