In December 2021, the companies postponed plans for an EUA application, due to initially disappointing trial results for the first two doses. The companies said that reliable data about the effectiveness and safety of a third dose of a three-dose regime might not be ready before April. Under outside pressure, the FDA, nevertheless, had weighed greenlighting the first two doses before receiving data on the third.

On Feb. 11, the agency abruptly pulled plans to begin the review earlier. “Being able to begin evaluating initial data has been useful in our review of these vaccines, but at this time, we believe additional information regarding the ongoing evaluation of a third dose should be considered,” acting commissioner Janet Woodcock said in a statement.

“Imagine us approving it after two doses and then finding out later that the third dose was unsafe and having to pull back,” advisory panel member Paul Offit, director of the Vaccine Education Center at Children’s Hospital of Philadelphia, told US media.

In mid-January, more than 5,000 children were hospitalized as the Omicron wave rolled across the country, and parents’ groups along with some physicians, had urged the FDA to authorize a vaccine for young children as soon as possible. Meanwhile, the wave seems to have peaked, with last week’s numbers at around 3,000.

During earlier trials, Pfizer and BioNTech said they found that two doses of the 3-microgram shot, one-tenth of the dose that older children and adults receive, did not produce an adequate immune response in children aged two to four. In December, the partners amended an ongoing trial with a two-dose regime to study a three-dose course.

Author: Dede Williams, Freelance Journalist