Knowledge from NIH mix-and-match Covid vaccine booster trials prepared quickly

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, gives an opening statement during a Senate Health, Education, Labor and Pensions Committee hearing to discuss the on-going federal response to COVID-19, at the U.S. Capitol in Washington, D.C., May 11, 2021.

Greg Nash | Pool | Reuters

White House chief medical advisor Dr. Anthony Fauci said Tuesday that safety and efficacy data on pairing a primary regimen of Covid vaccines from one manufacturer with boosters from another could be available within the next two weeks.

Though the Centers for Disease Control and Prevention authorized Pfizer’s booster for seniors and the medically vulnerable Friday, only recipients of Pfizer’s first two doses are eligible for the third shot. But the National Institutes of Health is on the verge of concluding trials that mixed boosters and initial doses from Pfizer, Moderna and Johnson & Johnson, Fauci said at a White House Covid briefing.

“As with all things we do, they must be submitted to the FDA for their regulatory approval,” Fauci said of the so-called mix-and-match trials. “So you don’t want to get ahead of the FDA, but at least that’s where the data are right now.”

Data on Johnson & Johnson’s mix-and-match study could be ready within a week, while Pfizer’s trial might be completed by mid-October. Moderna’s mix-and-match study data is already available, Fauci added.

Pfizer’s and Moderna’s vaccines employ mRNA technology to combat Covid, while J&J’s uses an adenovirus to bolster the body’s immune response. The ability to mix and match vaccines and boosters could give vaccine recipients greater flexibility in picking a third shot to strengthen the waning immunity of their initial doses.

Fauci’s comments came just days after NIH Director Dr. Francis Collins said the agency was still reviewing the results of combining initial doses and boosters from separate vaccine makers. Collins added that Moderna and J&J were weeks away from the CDC and FDA evaluating their boosters.

The NIH announced the start of its mix-and-match vaccine trials on June 1, which included roughly 150 adults who were vaccinated with Pfizer, Moderna or J&J. The participants were boosted with a different third dose approximately three to four months after receiving their initial vaccine regimen.