‘Mix and Match’?  Study Supports Following J&J Vaccine With Pfizer, Moderna

THURSDAY, Oct. 14, 2021 (HealthDay News) -- Americans who got Johnson & Johnson's single-dose coronavirus vaccine may be better protected if they get a booster shot from Pfizer or Moderna, preliminary findings from a new government study suggest.

Published on the preprint server medRxiv and yet to be peer-reviewed, the National Institutes of Health study found mixing different coronavirus vaccines was safe and effective, but booster shots made by Moderna and Pfizer produced more robust immune responses than Johnson & Johnson's booster shots did.

The findings will be presented to a U.S. Food and Drug Administration advisory panel on Friday, the second of two days of meetings where the emergency use authorization of booster shots from Moderna and Johnson & Johnson will be weighed by vaccine experts.

Whether the FDA might authorize the mix-and-match approach is unclear, The New York Times reported. The strategy will be discussed during the Friday meeting, but no vote will be taken. If regulators come to the conclusion that there is enough science to support the approach, they would likely need to update the authorization language of the Moderna and Pfizer-BioNTech vaccines to allow for their use in people who first received Johnson & Johnson's shot.

In the NIH study, researchers looked at nine groups of roughly 50 people each. Each group received one of the three authorized vaccines, followed by a booster. In three groups, volunteers received the same vaccine for a boost. In the other six, they got a different vaccine.

The differences were startling: Those who got a J&J shot followed by a Moderna booster saw their antibody levels rise 76-fold within 15 days, while those who got a second dose of the J&J vaccine saw only a fourfold rise during the same period. A Pfizer booster shot raised antibody levels in Johnson & Johnson recipients 35-fold. The Moderna and Pfizer vaccines are both mRNA vaccines, while the J&J vaccine uses an adenovirus to deliver the vaccine to the immune system.

"These data suggest that if a vaccine is approved or authorized as a booster, an immune response will be generated regardless of the primary COVID-19 vaccination regimen," the researchers wrote in the study.

Still, the NIH researchers noted the study's small size and added that volunteers haven't been followed long enough to identify rare side effects. However, there were no immediate serious side effects tied to the booster shots, the researchers added. Two participants vomited after their boosters; one had received Moderna and the other J&J. Two other people who got a J&J booster reported fatigue or insomnia.

Scott Hensley, an immunologist at the University of Pennsylvania who was not involved in the new study, told the Times that the results are compelling. He noted, however, that the trial only looked at antibody levels, which aren't the sole measure of an immune system response.

"At the end of the day, folks having the Johnson & Johnson should probably get an mRNA booster," he said. "It's just a matter of how much data does the FDA need before making that recommendation? I wouldn't want to be in their shoes."

E. John Wherry, director of the Institute for Immunization at the University of Pennsylvania, said the findings suggest that boosters of the Pfizer or Moderna vaccines would be best for people who received the J&J vaccine. But the lower antibody levels measured after the J&J booster shot do not necessarily equal worse protection, he added.

"I don't think this is the end of the story," he told NBC News. "I think this is the beginning of the discussion."

Wherry added that the most important finding was that it is safe to mix different vaccines and boosters. Further studies will be able to provide more details about the performances of different combinations, he said.

The FDA has already authorized an additional shot of the Pfizer vaccine for Americans over 65, or those 18 to 65 with underlying health conditions or jobs that put them at higher risk. Moderna's booster shot application, which will be discussed on Thursday, may also win authorization even though only limited evidence suggests the power of the two-shot vaccine is waning.

Unlike Pfizer's and Moderna's two-shot vaccines, J&J had hoped to offer a one-shot solution to the pandemic. But its protection, at 72% in the United States, is not as robust as Moderna's and Pfizer's vaccines, which have both touted efficacy rates well above 90%, CNBC reported.

However, a second dose of J&J's shot does boost protection from symptomatic infection to 94% when administered two months after the first dose in the United States, according to company data released in September.

In a separate document published on Wednesday, the FDA said data provided by J&J suggests recipients may benefit from an additional dose given two months after the initial shot.

More information

Visit the U.S. Food and Drug Administration for more on COVID vaccines.