The Food and Drug Administration may soon allow Americans to choose a different brand of booster for their next shot of a COVID-19 vaccine, the New York Times has reported. The regulator will likely package assent to the “mix and match” approach into its authorization of the Johnson & Johnson and Modern boosters expected to come this week. (The FDA has already authorized boosters of the Pfizer vaccine for high-risk people and those over 65 in September.)

The expected announcement will follow a federally funded vaccine study, that showed people who got Johnson & Johnson’s COVID-19 vaccine had a stronger immune response when boosted with Moderna and Pfizer. Experts did emphasize the short-term nature of the study, and its small sample size, advising caution when citing its outcomes.

A biostatistician on the FDA’s expert committee warned Friday that allowing recipients to pick a different brand of vaccine for their booster could be “very, very messy in terms of the messaging.” The regulatory agency may recommend sticking to the same vaccine as a booster where possible, sources familiar with the plan told the Times. The FDA declined to comment on the matter.