A lower dose of the Pfizer-BioNTech coronavirus vaccine — one-third the amount given to adults and teens — is safe and triggered a robust immune response in children as young as 5 years old, the drug companies announced in a news release Monday morning.

The finding, eagerly anticipated by many parents and pediatricians, is a crucial step toward the two-shot coronavirus vaccine regimen becoming available for younger school-aged children, perhaps close to Halloween.

The companies still must prepare and submit the data to the Food and Drug Administration, a process they expect to complete by the end of September. Then, the data — not yet published or peer reviewed — will be scrutinized by regulators to ascertain that the vaccine is safe and effective. That could take weeks, or up to a month.