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Omicron Protection Data from Mix-and-Match Jabs Coming Next Week

Dec. 21, 2021, 5:56 PM

Data on how much protection a Pfizer or Moderna booster after an initial Johnson & Johnson shot offers against the omicron variant should be available within the next week, the NIH’s lead scientist on the study said.

Covid-19 booster studies involving three of the same type of shot have consistently shown that an additional dose increases antibody levels to protect against the new strain, said Emily Erbelding, director of the microbiology and infectious diseases division in the National Institute of Allergy and Infectious Diseases, part of the National Institutes of Health. She said she expects results from the NIH’s mix-and-match study to move in that direction as well.

“It’s tending to follow the same pattern,” Erbelding said in an interview Tuesday. “Everything we’re seeing shows that omicron doesn’t neutralize as well but boosting gives you neutralization just to a lower level than prior variants.”

Researchers at the NIAID are expanding their work on mix-and-match studies as the omicron variant has become the dominant strain in the U.S., accounting for 73% of new Covid-19 cases compared to just 3% last week. Pfizer Inc. and its partner BioNTech SE as well as Moderna Inc. have released preliminary data indicating a booster dose increases antibody levels against omicron. J&J is collecting antibody and cellular data in the coming weeks on the impact of the variant on its vaccine.

But those studies evaluate what’s known as homologous boosting, or using the same type of vaccine for both the initial vaccination and the booster. Erbelding’s team will provide important information after the Food and Drug Administration made mix-and-match boosters an option in October.

More than 70% of people who got a booster after J&J received a messenger RNA vaccine, according to Centers for Disease Control and Prevention data. The agency recommended Pfizer or Moderna boosters for anyone who received a J&J vaccine as part of an overall recommendation to opt for an mRNA vaccine when possible—although that decision stems from concerns about a rare but serious blood clot and isn’t rooted in protection against Covid-19.

“If people are wondering what they should do or are contemplating what their next move is,” Erbelding said, “They should go with CDC recommendations.”

Initial Results

NIAID scientists released results in October that found a full dose of Moderna after J&J offered the best antibody response against Covid-19, bolstering neutralizing antibodies 76-fold over 15 days. A Pfizer booster after J&J led to a 35-fold increase in antibodies, and a second shot of J&J bolstered antibodies four-fold.

Erbelding noted Tuesday that the findings of her team aren’t comparing the messenger RNA platform to J&J’s, which uses a different, harmless virus to send instructions to the immune system on how to fight off the virus that causes Covid-19. One study indicated J&J’s vaccine may be slower at revving up antibodies but provides durable protection.

Since those initial data came out two months ago, the research team added another study arm that looks at a 50-microgram dose booster of Moderna’s vaccine. The original study design used 100-microgram doses, which is the same level as the two primary shots.

Until new data on omicron’s impact come out, Erbelding said everyone should take the recommendation to get boosted seriously.

“They should continue to do what they can with masking and avoiding crowds and doing things outdoors when they can. All of those practices are still very, very wise in the current era. But I think they should feel confident that they did the right thing by getting a booster,” she said.

To contact the reporter on this story: Jeannie Baumann in Washington at

To contact the editors responsible for this story: Alexis Kramer at; Karl Hardy at