Pfiz­er asked U.S. reg­u­la­tors Mon­day to ex­pand use of its up­dat­ed COVID-19 boost­er shot to chil­dren ages 5 to 11.

El­e­men­tary school-aged chil­dren al­ready re­ceived kid-sized dos­es of Pfiz­er’s orig­i­nal vac­cine, a third of the dose giv­en to every­one 12 and old­er -- two pri­ma­ry shots plus a boost­er.

If the Food and Drug Ad­min­is­tra­tion agrees, they would start get­ting a kid-sized dose of the new omi­cron-tar­get­ed for­mu­la when it was time for their boost­er.

FDA vac­cine chief Dr. Pe­ter Marks said last week he ex­pect­ed a de­ci­sion on boost­ers for that age group soon.

Pfiz­er and its part­ner BioN­Tech al­so an­nounced a new study of the omi­cron-fo­cused boost­er in even younger chil­dren, those ages 6 months through 4 years, to test dif­fer­ent dos­es.

Up­dat­ed boost­ers made by both Pfiz­er and ri­val Mod­er­na rolled out ear­li­er this month for every­one 12 and old­er. They’re a tweak to vac­cines that al­ready have saved mil­lions of lives -- a com­bi­na­tion or “bi­va­lent” shot that con­tains half the orig­i­nal recipe and half pro­tec­tion against the BA.4 and BA.5 omi­cron rel­a­tives re­spon­si­ble for most of to­day’s COVID-19 cas­es.

The hope is that the mod­i­fied boost­ers will help tamp down con­tin­u­ing COVID-19 cas­es and blunt an­oth­er win­ter surge. As of last week, the Cen­ters for Dis­ease Con­trol and Pre­ven­tion said 4.4 mil­lion Amer­i­cans had got­ten an up­dat­ed boost­er so far.

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The As­so­ci­at­ed Press Health and Sci­ence De­part­ment re­ceives sup­port from the Howard Hugh­es Med­ical In­sti­tute’s De­part­ment of Sci­ence Ed­u­ca­tion.

The AP is sole­ly re­spon­si­ble for all con­tent.