That could change by the first half of 2022, according to a chart highlighting upcoming company milestones that was included in Pfizer’s third-quarter earnings presentation in early November. Within the chart, which is on slide 29 of the presentation, Pfizer identifies target dates for “key approvals” (regulatory approval of drugs in the pipeline) and “key pivotal readouts” (results from ongoing drug trials).

According to that chart, Pfizer is targeting the fourth quarter of 2021 for the initial data readout regarding its COVID-19 vaccine for children between ages 2 and 5. Furthermore, the company aims to be presenting early data on its COVID-19 vaccine for kids between 6 months and 2 years of age in the first half of 2022.

Assuming Pfizer is able to meet those self-imposed deadlines, the company would hope to secure regulatory approval in the first half of 2022 for the vaccine for 2- to 5-year-olds and in the second half of 2022 for the vaccine for those between 6 months and 2 years. That would make roughly 25 million more children eligible for a COVID-19 vaccine by the second half of next year, according to childstats.gov, which keeps track of child population numbers in the U.S.

Pfizer had previously stated in prior press releases that initial efficacy and safety data for both age groups were “expected as soon as the fourth quarter of this year.”

Pfizer and BioNTech have been testing vaccines for these two age groups in a clinical trial alongside the recently approved shot for children ages 5 to 11. They’ve been testing a two-dose schedule (administered three weeks apart) of a three-microgram dose in children under the age of 5, which is smaller than the 10-microgram dose being given to children ages 5 to 11. That 10-microgram dose is already only one-third of what Pfizer and BioNTech are administering to everyone older than 12.

There are a few reasons why vaccines for young kids are taking longer. “With the COVID-19 vaccine, for example, we need to make sure it doesn’t interfere with immunity generated by routine childhood vaccinations—and that standard vaccination protocols are not interfering with the COVID-19 vaccine,” said Moshe Arditi, academic director of the division of pediatric infectious diseases at Cedars-Sinai, in an interview. “And that’s going to take some time to assess.”

In late October, Pfizer and BioNTech announced that the U.S. government had purchased 50 million more doses of the companies’ COVID-19 vaccine. According to the press release, the government will be using these additional doses “to support preparedness for pediatric vaccinations, including securing vaccines for children under 5 years of age, should they receive regulatory authorization.” The companies said they expect to deliver all those doses by April 30, 2022.

“We are extremely proud to provide enough doses of our vaccine to help protect every U.S. child under 12 from COVID-19, if authorized by the FDA,” Albert Bourla, who serves as the chairman and chief executive officer of Pfizer, said in a statement. “As we await…clinical trial results in children under 5, we are working with the U.S. government to help ensure communities across the country have access to pediatric doses as soon as possible. The introduction of doses for young children will be another critical milestone in addressing this public health crisis.”