Pfizer and BioNTech announced on Friday that the companies will modify a clinical trial for their coronavirus vaccine in young children, after a two-dose regimen did not produce a sufficient immune response in children ages 2, 3, and 4.
The companies said that “no safety concerns were identified” in the trial, and that participants age 2-4 will be given a third vaccine dose two months after their second dose. Participants ages six months to 24 months saw a sufficient immune response from the vaccine.
Participants were given 3 micrograms of vaccine, or one-tenth of the dose given to adults over age 18. Pfizer spokeswoman Jerica Pitts said the companies do not plan to increase the dosage for young children, and instead will determine whether a third 3-microgram dose generates sufficient immunity.
“The goal here is to understand the potential of protection of the third dose,” Pitts told the New York Times.
Pfizer still expects to request emergency authorization for the vaccine in children under 5 before summer 2022.
“It is important to note that this adjustment is not anticipated to meaningfully change our expectations that we would file for emergency use authorization and conditional approvals in the second quarter of 2022,” Kathrin Jansen, head of vaccine development at Pfizer, told investors in a call reported by the Washington Post.
The Pfizer coronavirus vaccine, developed jointly with BioNTech, is the only coronavirus vaccine authorized for Americans ages 5 and up. The Moderna and Johnson & Johnson Covid vaccines are authorized for Americans age 18 years and older.