(The Hill) — Pfizer and BioNTech said Friday they expect to submit an application for the use of their COVID-19 vaccine in children under five years old in the “first half of 2022” as they test a third dose for the age group. 

Pfizer said it is studying a third small dose of its vaccine for children under 5, given that the testing so far showed that the immune response with two small doses was not as high as desired in children 2 to 4 years old. 

The company added that no safety concerns have been identified so far. 

Children under 5 are currently the only age group where vaccines are not available, and many families eagerly await their introduction. That moment, however, might not come until sometime toward the middle of next year. 

“The decision to evaluate a third dose of 3 µg for children 6 months to under 5 years of age reflects the companies’ commitment to carefully select the right dose to maximize the risk-benefit profile,” Pfizer and BioNTech said. “If the three-dose study is successful, Pfizer and BioNTech expect to submit data to regulators to support an Emergency Use Authorization (EUA) for children 6 months to under 5 years of age in the first half of 2022.”

White House medical adviser Anthony Fauci said last month that he had hoped the vaccine for children under 5 would be available “likely the beginning of next year in 2022, in the first quarter of 2022,” though he noted the timeline depended on results of the clinical trial. 

Pfizer also said Friday it is testing a third dose in children 5 to 12 and 12 to 17, as experts urge adults to get a booster shot.