Two doses of Pfizer's COVID-19 vaccine adjusted in potency for children 5 to 11 years old proved 90.7% effective against symptomatic disease, the company said in documents filed with the government, as U.S. authorities near key decisions on whether to expand use of the shots to younger age groups.
The estimate comes from early results of the company's trials of the vaccine in more than 2,000 participants from 5 to 11 years old, which were released Friday as part of the company's submission to the Food and Drug Administration's outside vaccine advisers.
The advisers are scheduled to meet on Tuesday next week to weigh in on whether the FDA should grant emergency use authorization for the shots in younger American children. Currently, Pfizer's vaccine is only permitted for use in adolescents 12 years and older.
More documents are expected to be posted ahead of the meeting of the FDA's Vaccines and Related Biological Products Advisory Committee, including an independent review by the FDA of the company's data. The panel is also scheduled to hear updates Tuesday from other federal officials about the state of the pandemic and vaccine before they vote on the shots.
Pfizer says data from its trials spanning two groups in the age range, totaling some 4,500 children between 5 and 11 years old, also show the vaccine is likely to be safe in its new pediatric formulation, with only "mild to moderate" side effects seen in most recipients of the smaller 10-microgram dose of its vaccine it has formulated for younger children.
The company says it decided on the smaller shots after use of a 30 microgram dose — which is used in adolescents and adults — triggered far worse side effects.
Nearly all children under 12 in the company's small "dose-ranging" study given the full dose of the vaccine experienced reactions like moderate or severe fatigue, muscle pain, redness, and pain at the injection site, far more in most cases than for those who were given the smaller 10 microgram dose that the company is now pursuing.
Trials run by the company also turned up no "new safety concerns" for the smaller dose in the younger children, according to Pfizer.
The company acknowledged it's likely the trials are too small to truly assess the risks of some rare side effects like myocarditis and pericarditis, which have been linked to the shots in adults and adolescents who have received the vaccine. But it cited safety surveillance conducted in Israel — which rolled out Pfizer's vaccine for adolescents nationwide earlier this year — that suggest rates of this kind of heart inflammation in younger children after the shots "are likely to be even lower" than in adults.
While some parents have been clamoring for the FDA to greenlight COVID-19 vaccines for younger children, some of the FDA's vaccine advisers previously expressed skepticism over whether the benefits of the shots would clearly outweigh their risks for younger age groups — especially as cases appear to decline nationwide.
In its submission, Pfizer argues that all children - regardless of underlying conditions that might raise their risk of severe COVID-19 - should receive the shot, citing the recent surge in cases, hospitalizations, and deaths amid the Delta variant which have far outpaced the toll of the flu.
"There is a concern that we may need to really get the maximum vaccination in place of as many people, including the younger children, in order to really get this pandemic under control," Dr. Peter Marks, the FDA's top vaccines official, told a webinar hosted by the group Made to Save earlier this month.
While children are generally less likely to see a severe case of COVID-19, a growing body of research has demonstrated that they are just as likely to catch and spread the disease as adults even before the fast-spreading Delta variant.
Federal and local health officials are already anticipating the shot's authorization by the FDA and Centers for Disease Control and Prevention and have begun to prepare for rollout of the new doses for younger children.
"Operationally, if authorized by the FDA and CDC, we will be ready. As we talked about, we have the supply," Jeff Zients, the White House's top COVID-19 official, told reporters this week.
Providers have already begun placing orders for shipments of the doses, which will be packaged in different vials than the adult shots. Fifteen million doses will be allocated for distribution in the first week following authorization, according to White House officials, enough to begin vaccination in the majority of the 28 million children who could become eligible.
According to planning documents posted by the CDC, Pfizer's new formulation for younger kids could last 10 weeks after thawing from frozen — more than double the shelf life of the current adult vials — in a vaccine provider's refrigerator.
The White House and federal health officials will also be launching outreach campaigns to inspire confidence in the shots for younger children and parents, as well as to recruit more vaccine providers who can reach them — like family doctors and school nurses.
"We'll make it convenient and easy for parents and kids by bringing vaccines to pediatricians' offices, schools, rural health clinics, pharmacies, and children's hospitals," said Zients.