Small doses of Pfizer’s COVID-19 mRNA vaccine in children ages 5 to 11 appeared to produce strong antibody responses and comparable side effects to those seen in older age groups, according to the first top-line results from a Phase 2/3 clinical trial released by Pfizer and its partner BioNTech early Monday.
The trial data involved 2,268 children ages 5 to 11 years, and these children were given a series of two 10-microgram doses of the vaccine, 21 days apart. The dosage is just a third of the 30-microgram doses given to people ages 12 and above.
One month after the second dose, researchers measured the children’s levels of antibodies able to neutralize SARS-CoV-2 virus in a lab experiment. The geometric mean titer of antibody in the 5 to 11 year olds was 1,197.6 (95 percent confidence interval of 1,106.1 to 1,296.6), which is comparable to the geometric mean titer of 1,146.5 seen in people ages 16 to 25.
Pfizer described the vaccine as being well tolerated in children, with side effects generally comparable to what’s seen in people ages 16 to 25. But the company did not provide further data on the side effects.
It also did not provide any further data on vaccine efficacy, though experts expect that comparable neutralizing antibody levels will provide comparable levels of protection against infection, hospitalization, and death.
In an announcement this morning, Pfizer said it plans to submit the data to the US Food and Drug Administration, European Medicines Agency, and other regulators as soon as possible and “before the start of the winter season.” William Gruber, Pfizer’s senior vice president of vaccine clinical research and development, told Stat news that the company aims to submit the data for emergency use authorization to the FDA by the end of this month.
Once data is submitted to the FDA, it will take regulators several weeks to review the data and make a decision. That places the earliest estimates for vaccine authorization and availability for the 5-to-11 group at the end of October.
That timeline is largely in line with what Pfizer and US officials have said before. The company has also estimated that it will be ready to submit vaccine data for even younger children—ages 6 months to 5 years—about a month later, in the early November timeframe. If all goes well, that could put vaccine availability for that youngest group around the start of December.
“Since July, pediatric cases of COVID-19 have risen by about 240 percent in the US—underscoring the public health need for vaccination,” Pfizer CEO Albert Bourla said in a statement. “These trial results provide a strong foundation for seeking authorization of our vaccine for children 5 to 11 years old, and we plan to submit them to the FDA and other regulators with urgency.”