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COVID-19 Resource Center

Disclosures: The authors report no relevant financial disclosures. Research funding was provided by the National Institute of Allergy and Infectious Diseases.
January 26, 2022
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Results of NIH mix-and-match COVID-19 booster trial published

Disclosures: The authors report no relevant financial disclosures. Research funding was provided by the National Institute of Allergy and Infectious Diseases.
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The New England Journal of Medicine on Wednesday published data from the ongoing NIH-sponsored trial that led the FDA last fall to authorize the mix-and-match strategy for COVID-19 vaccine boosters.

The NIH said more data from the phase 1/2 trial are expected to be available “in the coming months.”

booster graphic

Results from the trial, which showed that receiving a booster dose of a different vaccine was as good or better than receiving another dose of the same vaccine as your initial series, were previously published on the pre-print server medRxiv.

The FDA authorized the mix-and-match strategy in October and the CDC endorsed the approach in federal guidelines, allowing vaccinated Americans to choose their own booster shot.

“In this preliminary trial, we found that boosting with any of the three vaccines that are currently authorized for emergency use in the United States will stimulate an anamnestic response in persons who have previously received a primary series of any of these vaccines,” Robert L. Atmar, MD, professor of infectious diseases at Baylor College of Medicine in Houston, and colleagues wrote in the study.

They enrolled 458 participants in the trial from May 29 to Aug. 13, 2021, at 10 sites in the U.S. All participants had completed a COVID-19 vaccine regimen at least 12 weeks earlier and received one of the three authorized vaccines as a booster — 153 received a booster dose of the Pfizer vaccine, 154 received a booster dose of the Moderna vaccine, and 150 received a booster dose of the Johnson & Johnson vaccine. (One participant did not receive an assigned vaccine.)

According to the authors, in all combinations of vaccine, antibody neutralizing titers against SARS-CoV-2 increased by a factor of 4 to 73, and binding titers increased by a factor of 5 to 55.

Among any participant who received one of the two messenger RNA vaccines as a booster, between 96% and 100% experienced an increase in the binding antibody titer by a factor of 2 or more, no matter which initial vaccine series they completed.

Homologous and heterologous booster vaccines had an acceptable safety profile and were immunogenic in adults who had completed a primary COVID-19 vaccine regimen at least 12 weeks earlier,” the authors wrote.