By LAU­RAN NEER­GAARD and MATTHEW PER­RONE | AS­SO­CI­AT­ED PRESS 

WASH­ING­TON (AP) — Pfiz­er on Tues­day asked the U.S. to au­tho­rize ex­tra-low dos­es of its COVID-19 vac­cine for chil­dren un­der 5, po­ten­tial­ly open­ing the way for the very youngest Amer­i­cans to start re­ceiv­ing shots as ear­ly as March.

In an ex­tra­or­di­nary move, the Food and Drug Ad­min­is­tra­tion had urged Pfiz­er and its part­ner BioN­Tech to ap­ply ear­li­er than the com­pa­nies had planned — and be­fore it’s set­tled if the young­sters will need two shots or three.

The na­tion’s 19 mil­lion chil­dren un­der 5 are the on­ly group not yet el­i­gi­ble for vac­ci­na­tion against the coro­n­avirus. Many par­ents have been push­ing for an ex­pan­sion of shots to tod­dlers and pre-school­ers, es­pe­cial­ly as the omi­cron vari­ant sent record num­bers of young­sters to the hos­pi­tal.

“I would say the par­ents in my of­fice are des­per­ate” to get young kids vac­ci­nat­ed, said Dr. Dyan Hes, who runs a pae­di­atrics prac­tice in New York City, where vac­ci­na­tion rates are high. For many, “that’s the first thing they ask when they walk through the door: ‘When do you think the shot is go­ing to come out?’”

Pfiz­er aims to give chil­dren as young as 6 months shots that con­tain one-tenth of the dose giv­en to adults. The com­pa­ny said it had start­ed sub­mit­ting its da­ta to the FDA and ex­pects to com­plete the process in a few days.

An open ques­tion is how many shots those chil­dren will need. Two of the ex­tra-low dos­es turned out to be strong enough for ba­bies but not for pre-school­ers in ear­ly test­ing. Pfiz­er now is test­ing a third shot, da­ta that’s ex­pect­ed in late March.

That means the FDA may con­sid­er whether to au­tho­rize two shots for now, with po­ten­tial­ly a third shot be­ing cleared lat­er if the study sup­ports it.

Pfiz­er CEO Al­bert Bourla said in a state­ment that com­pa­ny sci­en­tists be­lieve this age group ul­ti­mate­ly will need three of the ex­tra low-dose shots, but that FDA ac­tion now could let par­ents be­gin the vac­ci­na­tion process while await­ing a fi­nal de­ci­sion.

The FDA said it will con­vene a pan­el of in­de­pen­dent re­searchers and physi­cians in mid-Feb­ru­ary to help re­view the Pfiz­er da­ta. The agency isn’t re­quired to fol­low their ad­vice, but the in­put is a key step in pub­licly vet­ting vac­cine safe­ty and ef­fec­tive­ness.

The ques­tion of how long to wait for new vac­cine da­ta — and how much to re­quire — is a con­cern for FDA reg­u­la­tors, who face pres­sure to be more proac­tive against a virus that has re­peat­ed­ly con­found­ed health ex­perts.

The FDA asked Pfiz­er to be­gin sub­mit­ting its ap­pli­ca­tion now due to omi­cron’s “greater toll on chil­dren,” an agency spokes­woman said, cit­ing a peak in cas­es among chil­dren un­der 5.

“In light of these new da­ta and the rise in ill­ness­es and hos­pi­tal­iza­tion in this youngest age group, FDA be­lieved that it was pru­dent to re­quest that Pfiz­er sub­mit the da­ta it had avail­able,” agency spokes­woman Stephanie Cac­co­mo said in an emailed state­ment.

The FDA’s ul­ti­mate de­ci­sion could come with­in the month, but that isn’t the on­ly hur­dle. The Cen­ters for Dis­ease Con­trol and Pre­ven­tion al­so has to sign off.

The Biden ad­min­is­tra­tion has been try­ing to speed the au­tho­riza­tion of COVID-19 shots for chil­dren, con­tend­ing vac­ci­na­tions are crit­i­cal for open­ing schools and day care cen­tres and keep­ing them open, and for free­ing up par­ents from child­care du­ties so they can go back to work.

Yet vac­ci­na­tion rates have been low­er among chil­dren than in oth­er age groups. As of last week, just 20% of kids ages 5 to 11 and just over half of 12- to 17-year-olds were ful­ly vac­ci­nat­ed, ac­cord­ing to the Amer­i­can Acad­e­my of Pe­di­atrics. Near­ly three-quar­ters of adults are ful­ly vac­ci­nat­ed.

Young chil­dren are far less like­ly than adults to get se­vere­ly ill from the coro­n­avirus, but it can hap­pen, and pae­di­atric COVID-19 in­fec­tions are high­er than at any oth­er point in the pan­dem­ic.

“What we’re see­ing right now is still a lot of hos­pi­tal­iza­tions and un­for­tu­nate­ly some deaths in this age group,” said Dr. Sean O’Leary of the Uni­ver­si­ty of Col­orado, who is on the AAP’s in­fec­tious dis­ease com­mit­tee. If the FDA clears vac­ci­na­tions for these young­sters, “that’s go­ing to be re­al­ly im­por­tant be­cause all of those hos­pi­tal­iza­tions and deaths es­sen­tial­ly are pre­ventable.”

For kids un­der 5, Pfiz­er’s study is giv­ing par­tic­i­pants two shots three weeks apart, fol­lowed by a third dose at least two months lat­er. The com­pa­ny is test­ing whether the young­sters pro­duce an­ti­body lev­els sim­i­lar to those known to pro­tect teens and young adults.

In De­cem­ber, Pfiz­er an­nounced that chil­dren un­der 2 looked to be pro­tect­ed but that the an­ti­body re­sponse was too low in 2- to 4-year-olds. It’s not clear why, but one pos­si­bil­i­ty is that the ex­tra-low dose was a lit­tle too low for the pre-school­ers.

Since the pre­lim­i­nary re­sults showed the shots were safe, Pfiz­er added a third dose to the test­ing in hopes of im­prov­ing pro­tec­tion.

A Kaiser Fam­i­ly Foun­da­tion poll found just 3 in 10 par­ents of chil­dren un­der 5 would get their young­ster vac­ci­nat­ed as soon as shots were au­tho­rized, while about a quar­ter said they def­i­nite­ly would not. Re­sults of the sur­vey of 1,536 adults, con­duct­ed in mid-Jan­u­ary, were re­leased Tues­day.

Chica­go health of­fi­cials have been try­ing to pre­pare par­ents for months for the day the shots are avail­able, said Dr. Nim­mi Ra­jagopal, a fam­i­ly med­i­cine physi­cian for Cook Coun­ty Health, which over­sees the pub­lic hos­pi­tal sys­tem. Some par­ents won­der how rig­or­ous­ly the shots will be eval­u­at­ed or have oth­er ques­tions that she said are crit­i­cal to ad­dress.

Ra­jagopal is ex­cit­ed about get­ting her own 2-year-old son vac­ci­nat­ed if FDA clears the way, so it will be safer for him to play with oth­er chil­dren.

“I have been wait­ing and wait­ing and wait­ing,” she said.

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As­so­ci­at­ed Press jour­nal­ists Em­ma H. To­bin and Mike Sto­bbe con­tributed to this re­port.