Babies as young as 6 months could get a COVID-19 vaccine in a few weeks in the US if regulators agree vaccines are safe and effective for that age group.

On Tuesday, Pfizer and BioNTech took the first major step that could truly make their COVID-19 vaccines available to children when they submitted data from their clinical trials to the Food and Drug Administration for review. There are still some regulatory steps ahead, but things could move quickly from here. For comparison: last fall's trial with children aged 5 to 11 lasted just over four weeks.

The following must happen before children under the age of 5 can start vaccination against COVID-19.

It remains to be seen whether parents will be willing to accept the vaccines once they are approved. According to a survey released Tuesday by the Kaiser Family Foundation, more than two-thirds of parents of children in this age group say they will wait or "definitely" not plan to vaccinate their children. Almost a third of parents say they will have their babies and toddlers vaccinated immediately.

Pfizer is currently further along in the approval process, but Moderna is also testing its vaccine in this age group: the company plans to submit data on children aged 2 to 5 to the FDA in March. Johnson & Johnson is also expected to conduct infant vaccine trials in the future.