Pfizer Says Its Low-Dose Vaccine Doesn’t Work in Kids Aged 2–5

To test 3rd COVID-19 shot for kids under 5

A nurse prepares a dose of a COVID-19 vaccine to be injected at the Andras Josa Teaching Hospital in Nyiregyhaza, Hungary, on Jan. 24, 2021. (Attila Balazs/MTI via AP, File)

A low dose of the Pfizer-BioNTech COVID-19 vaccine didn’t produce a significant immune response among children between the ages of 2 and 5, the two firms said on Friday.

Amid clinical trials that are ongoing, the two drugmakers tested 3 micrograms of the vaccine in kids aged 6 months to less than 5 years of age. Children between 6 months and 2 years produced an immune response comparable to individuals aged 16 to 25 years after two adult doses of the mRNA vaccine (30 micrograms), the companies said.

However, the vaccine didn’t produce a significant immune response after the same low-dose regimen in children between the ages of 2 and 4, according to the companies. Pfizer and BioNTech said they will change their plans and will test three doses of their COVID-19 vaccine on children in that age group rather than the usual two doses.

Should the three-dose study prove successful, the companies said they will apply for an emergency use authorization from the Food and Drug Administration sometime in the first half of 2022.

“The study will now include evaluating a third dose of 3 [micrograms] at least two months after the second dose of the two-dose series to provide high levels of protection in this young age group,” the companies wrote in their statement. “No safety concerns were identified and the 3 [microgram] dose demonstrated a favorable safety profile in children 6 months to under 5 years of age,” they said.

On Thursday, the Centers for Disease Control and Prevention (CDC) confirmed it received reports of eight cases of myocarditis, a type of heart inflammation, in children between the ages of 5 and 11 years who received the Pfizer-BioNTech vaccine.

Those cases were reported via the U.S. Vaccine Adverse Event Reporting System, known as VAERS, and presented by the CDC to a panel of its advisers. The CDC didn’t say whether officials believe there’s a link between the myocarditis cases and the vaccine, and it did not disclose the rate of myocarditis in the same age group who were not vaccinated.

And a recent study found that two Pfizer vaccine doses may be more easily breached by the Omicron COVID-19 variant that reportedly emerged in southern Africa last month and is already in at least three-dozen U.S. states. A study from South Africa’s largest private health insurer, Discovery Ltd., found that Omicron reduced the vaccine’s effectiveness from 80 percent to 33 percent.

To date, the FDA has only authorized the Pfizer-BioNTech vaccine for emergency use in kids aged 5 and older. About a month ago, the agency authorized a booster dose of both the Pfizer and Moderna vaccine for all U.S. adults.

Meanwhile, boosters of the Pfizer vaccine for 16- and 17-year-olds were cleared last week by the FDA.