BNTX BioNTech SE

By Jared S. Hopkins 

Pfizer Inc. said Thursday it has started testing its Covid-19 vaccine in young children, a key step toward broadening vaccination efforts.

Researchers administered the first doses of the vaccine to children enrolled in the study, which is evaluating the shots in children six months to 11 years. Pfizer expects initial results by the end of the year.

The vaccine, which Pfizer developed with BioNTech SE, is authorized for use in people 16 years and older. Pfizer had earlier started testing the vaccine in children ages 12 years to 15 years.

Children appear to be at lower risk of contracting the coronavirus than adults. When they are infected, they tend to experience milder symptoms, though some get seriously ill and can spread the virus.

Children make up about 13% of Covid-19 cases in the U.S., according to the American Academy of Pediatrics.

Doctors and health authorities say it will be important to vaccinate children, not only to protect them from the virus but also to help reach the communitywide protection known as herd immunity.

"If you really want to vaccinate somewhere between 70% to 80% of the population to achieve herd immunity, neglecting a large component of the population isn't the right thing to do," said Emmanuel Walter, professor of pediatrics and chief medical officer of the Duke Human Vaccine Institute in Durham, N.C., which administered the vaccine to the first subjects Wednesday.

The Pfizer-BioNTech vaccine is among three authorized for use in the U.S., along with shots from Moderna Inc. and Johnson & Johnson.

Most of the Covid-19 vaccination efforts in the U.S. and abroad have focused on protecting older adults who are at higher risk of severe disease caused by the coronavirus than children.

The vaccines from Moderna and Johnson & Johnson are authorized in the U.S. for use in adults 18 years and older.

Both New York-based Pfizer and Moderna last year started testing their vaccines in children 12 years and older. J&J said it is in discussions with regulators to start pediatric testing of its vaccine, though it didn't give a timeline.

Pfizer expects to submit to regulators results from the trial evaluating the vaccine in children 12 to 15 years in the coming weeks, Pfizer Chief Executive Albert Bourla said Tuesday at The Wall Street Journal's Health Forum.

Similar to adult trials, researchers must recruit healthy volunteers to test the vaccines, but the process can be time-consuming because parental consent is needed, pediatricians said.

Earlier this month, Moderna began testing its shot in children 6 months to 11 years.

Pfizer's latest pediatric study will enroll up to 4,644 children in the U.S. and Europe. The young volunteers will receive two doses three weeks apart, as is the current dosing regimen.

Initially, researchers will test various doses in different age groups to find the most appropriate dose for further testing. Researchers will first evaluate doses in kids 5 to 11 years before moving onto children who are 2 to 5 years and finally, those 6 months to 2 years old.

After they settle on a dose for each age group, researchers will test the vaccine in more children. They will administer the vaccine to two-thirds of study subjects and give a placebo to the rest.

Pfizer said researchers will determine the vaccine's effectiveness in children in one of two ways.

One way would hinge on whether researchers could determine what level of immune response generated by the vaccine is sufficient to provide protection. If researchers can, they would measure whether young vaccinated subjects reached that so-called correlate of protection.

Researchers could also compare the response in the young study subjects to the response found in young adults in the vaccine's pivotal trial.

Write to Jared S. Hopkins at jared.hopkins@wsj.com

(END) Dow Jones Newswires

March 25, 2021 12:44 ET (16:44 GMT)

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