According to the AP, Pfizer announced the change after a preliminary analysis found 2- to 4-year-olds didn't have as strong an immune response as expected to the very low-dose shots the company is testing in the youngest children.

All of this seems funny to us off the bat because it was our understanding that youngsters had natural immunity to the virus barring some immunodeficiency issue.

Pfizer said  it had expected data on how well the vaccines were working in children under 5 by year's end. Now, nobody knows how long that might take as the company tries out different strategy. But one thing's for sure: Pfizer is about to be selling a lot more vaccines.

A kid-sized version of Pfizer's vaccine is already available for 5- to 11-year-olds, one that's a third of the dose given to adults and anybody else aged 12 and older.

For children younger than 5, Pfizer is testing an even smaller dose, just 3 micrograms or a tenth of the adult dose. Here's the quandry: The very low-dose shots appeared to work just fine in youngsters under age 2, who produced similar antibody levels. But the immune response in 2- to 4-year-olds was lower, according to Pfizer vaccine research chief Kathrin Jansen.

Oddly, rather than trying a higher-dose shot for the preschoolers, Pfizer decided to expand the study to evaluate three of the very low-dose shots in all the study participants - from 6 months up to age 5. This third shot will be given at least two months after the youngsters' second dose.

And the head researcher said if the additional pediatric testing is successful, "we would have a consistent three-dose vaccine approach for all ages."

We imagine Pfizer, Moderna and the rest of then would love that - selling 50% more doses to whoever's willing to buy them.