Low dose of Pfizer shot fails to protect kids in trial

NEW YORK • A low dose of the Pfizer-BioNTech coronavirus vaccine did not produce a potent immune response in children aged two to just under five, the companies have announced, a discouraging setback that threatens to keep the vaccine from younger children for longer than many parents had hoped.

In ongoing clinical trials, the companies tested three micrograms of the vaccine - one-tenth of the adult dose - in children six months to younger than five years of age.

After two doses, children between six months and two years old produced an immune response that was comparable to that of people aged 16 to 25, the companies said.

But children between two and five years old did not.

The companies said they were now going to test a third low dose of the coronavirus vaccine in children from six months to under five years of age.

But they do not plan to test a higher dose of the vaccine in children who are between two and five years of age.

"The goal here is to understand the potential of protection of the third dose," said Ms Jerica Pitts, a spokesman for Pfizer.

"We are studying three micrograms at this time."

In a conference call with investors and analysts on Friday, Dr Kathrin Jansen, Pfizer's head of vaccine research, said the company plans to seek authorisation for a "three-dose series" in children, instead of the originally planned two doses.

If the revised strategy works, "we would have a consistent three-dose vaccine approach for all ages", she said.

Early studies indicate that three doses of the mRNA vaccines may provide a stronger bulwark against the Omicron variant than two doses.

In the ongoing trial, children younger than five years will receive three micrograms of the vaccine at least two months after their second dose.

Pfizer and BioNTech also plan to evaluate a third dose of 10 micrograms - one-third of the adult dose - in children five and up to 12 years of age.

The changes have been cleared by the United States Food and Drug Administration (FDA) and the European Medicines Agency, according to a statement released by the companies on Friday. The companies say they would seek FDA authorisation for a three-dose series in younger children in the first half of next year.

NYTIMES