Large U.S. study confirms that mRNA boosters extend COVID-19 protection but wane over time, strongly supporting need for additional booster

A nationwide U.S. study of more than 893,000 adults provides solid evidence confirming that mRNA booster immunizations extend protection against moderate and severe COVID for four to five months. These findings, published in The BMJ, provide a more complete understanding of the effectiveness and durability of third and fourth doses of the mRNA vaccines, informing policymakers and providing individuals with confirmation of the importance and value of boosters.

Vaccine effectiveness provided by boosters waned less against severe disease than against moderate disease in all age groups according to the new study which was conducted by the Centers for Disease Control and Prevention’s (CDC) VISION Network.

“While there have been recommendations for booster shots for a while, until now we haven’t had strong evidence of their effectiveness and how long that effectiveness lasts,” said study co-author Brian Dixon, PhD, of the Regenstrief Institute and Indiana University Richard M. Fairbanks School of Public Health. “In our new study, we looked at tens of thousands of patients in multiple states, seen over a year and a half. Our analysis provides compelling evidence, both of the effectiveness of boosting to increase immunity, and that this immunity begins to wane after four or five months, indicating additional booster doses are necessary.

“The recommendations to get boosted that were issued by the CDC months ago, were, in fact, the right recommendations,” said Dr. Dixon. “Booster doses are necessary to maintain a high level of immunity to severe COVID.”

The bivalent booster, available since early September 2022, targets both historic strains of the SARS-CoV-2 virus and the Omicron variants (BA.4 and BA.5) currently circulating in the U.S. and globally.

Building on their initial, preliminary analysis, published in CDC’s Morbidity and Mortality Weekly Report, in the new study, the VISION Network scientists analyzed data from patients seen at 261 hospitals, 272 emergency departments and 119 urgent care clinics in 10 states across the U.S. from January 17, 2021 to July 12, 2022. The data covered periods of Omicron dominance (including subvariants BA.4 and BA.5), as well as the previous periods of Delta and pre-Delta dominance. The new study is published in The BMJ.

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