The government would not recommend one shot over another, and it might state that using the same vaccine as a booster when possible is preferable. But vaccine providers could use their discretion to offer a different brand.
On Oct. 15, researchers presented the findings of a federally funded “mix and match” study to an expert committee that advises the FDA. The study found that recipients of Johnson & Johnson’s single-dose shot who received a Moderna booster saw their antibody levels rise 76-fold in 15 days, compared with only a fourfold increase after an extra dose of Johnson & Johnson, the report noted.
The FDA is expected to authorize boosters of the Moderna and Johnson & Johnson vaccines by Wednesday evening and it could allow the mix-and-match approach by then. The agency last month authorized booster shots of the Pfizer-BioNTech vaccine for at least six months after the second dose.
An advisory committee of the Centers for Disease Control and Prevention will take up the booster issue on Thursday. The agency will then issue its own recommendations. By the end of the week, tens of millions more Americans could be eligible for extra shots.
The study presented to the F.D.A.’s advisory panel last week, conducted by the National Institutes of Health, suggested that Johnson & Johnson recipients might benefit most from a booster shot of the Moderna vaccine. A shot of the Pfizer-BioNTech vaccine also raised the antibody levels of Johnson & Johnson recipients more than Johnson & Johnson did, the study found, although not as much as Moderna did. The N.I.H. researchers tested a full dose of Moderna’s vaccine for a booster shot, but regulators are also considering whether to authorize a half dose, the report said.