Covid-19 booster shots from Moderna or Pfizer showed signs they are more effective at protecting vaccinated adults than a second dose of Johnson & Johnson’s vaccine, according to preliminary results from a government-funded study.
All of the participants in the National Institutes of Health study saw an antibody boost after receiving additional doses of the three vaccines. But people who originally received J&J benefited significantly more from a messenger RNA booster than a second J&J dose, according to the study. The increase in binding antibodies — one signal of an immune response — was greatest for those who initially were immunized with J&J’s shot but received one of the mRNA boosters.
The study evaluated a 100-microgram dose of Moderna’s vaccine as a booster, conflicting with that company’s bid to allow half that amount for its booster shot.
The findings could pose a challenge for the federal government, which has not yet recommended mixing vaccines but is expected to decide on whether to greenlight boosters for all available vaccines by the end of the month.
The Food and Drug Administration’s independent advisory panel on vaccines will vote on whether to recommend Moderna and J&J boosters this week, with an agency decision expected shortly thereafter. The committee will also consider the results of the mix-and-match study, though it’s not scheduled to make any recommendations on the approach.
The NIH study has not yet been peer-reviewed. The authors acknowledged limitations, including that the vast majority of participants were white and that the interval between when individuals received their primary vaccine series and their boosters was less than six months — the authorized threshold for the Pfizer-BioNTech shot.
Leana Wen, an emergency physician and public health professor at George Washington University, said the results show that mixing and matching boosters appears to be safe and effective.
“I hope that the FDA and CDC will consider these results in their deliberations and allow, in particular, for recipients of the Johnson & Johnson vaccine to receive an mRNA second dose,” said Wen, who participated in J&J’s single-shot trial and has advocated for widespread booster availability.
FDA last month authorized emergency use of Pfizer’s vaccine as a booster for people 65 and older and for people whose health conditions or jobs put them at greater risk of developing severe Covid. It could make a similar decision for Moderna this week.