But boosters are unlikely to slow the agency’s work in considering full approval for Covid-19 vaccines or authorization of a vaccine for children. As for the other two companies with authorized vaccines in the United States, Moderna has begun submitting data for approval of its two-dose vaccine, and Johnson & Johnson has not yet submitted data for full approval, but expects to do so. Pfizer has said it expects to have vaccine trial data on children ages 5 to 11 by the end of September, and the company could apply to have its vaccine authorized for those younger ages shortly after.