Testing a third dose will cause a delay in submission of data to regulators to authorize use in the U.S. In the fall, Pfizer’s CEO said the company expected to have data for this age group by the end of 2021. Now, the company says that they would expect to file results in the “first half of 2022” if trials are successful.

The companies said two doses did not produce a robust immune response in kids 2 to 5 years old…

“The study will now include evaluating a third dose of 3 [micrograms] at least two months after the second dose of the two-dose series to provide high levels of protection in this young age group,” the companies said in a statement.