Pfizer said Monday its COVID-19 vaccine safely protects children ages 5 to 11 and it will ask federal regulators to clear it for use in that age group soon, a significant potential milestone in the fight against a disease that has infected more than 42 million people and killed over 673,000 in the United States.
The vaccine made by the New York-based drug giant Pfizer and its German partner BioNTech is already available for anyone 12 and older. But with children back in school and the highly contagious Delta variant causing pediatric infections to surge, many parents and teachers are eager to get younger kids vaccinated — to protect them and others who have contact with them.
If regulators authorize the vaccine for emergency use, children ages 5 to 11 would get two shots three weeks apart, the same as other Pfizer vaccine recipients. But each dose would contain 10 micrograms of the messenger RNA vaccine, one-third of the current dose. Despite the smaller amounts given in the trial of 2,268 participants, Pfizer executives said, the shots resulted in coronavirus-fighting antibody levels just as robust as those in teenagers and young adults. (The company picked the smallest dose that elicits robust protection while causing the fewest side effects.)
The exact timeline for any rollout is unclear. But if the regulatory review for emergency use moves as swiftly as it did for the Pfizer shots in older children and adults, millions of elementary school students could be inoculated by Halloween.
“We are eager to extend the protection afforded by the vaccine to this younger population, subject to regulatory authorization, especially as we track the spread of the Delta variant and the substantial threat it poses to children,” Albert Bourla, Pfizer’s chief executive, said in a statement. “Since July, pediatric cases of COVID-19 have risen by about 240 percent in the US, underscoring the public health need for vaccination.”
The messenger RNA vaccine was tested on children at more than 100 trial sites in the United States and overseas, including on 38 children at Boston Medical Center.
“It’s very good news,” Dr. Elizabeth Barnett, a pediatric infectious diseases specialist who ran the trial at BMC, said of Pfizer’s announcement. About two-thirds of the subjects got the vaccine, one-third a placebo. “We found that most of the children tolerated the vaccine very well,” she said.
Dr. Gabrielle Jacquet’s 7-year-old daughter got the vaccine in March and experienced no side effects other than a red mark on her arm for a few days. Jacquet, an emergency physician at BMC, entered Pfizer’s vaccine trial on adults last year with her husband and immediately wanted to enroll her daughter when the children’s trial started.
“It’s really such a relief and an exciting piece of the puzzle to have Pfizer release their data,” she said. “My daughter is very, very proud... She [feels] like she is contributing to helping the safety of all children in the world.”
The most common side effect was soreness at the injection site, Barnett said, a frequently reported symptom in recipients of the more than 220 million Pfizer doses administered in the country. Other reported side effects included fatigue, muscle aches, and headaches. There were no serious side effects in Barnett’s trial.
Massachusetts officials say there are 884,000 children under the age of 12 in the state, including 515,000 who are ages 5 to 11.
BMC has also tested the Pfizer vaccine, at a 3-microgram dosage, in a study involving 13 children ages 2 to 4, which is part of a bigger trial onthat age group. The results have not been released.
Neither Pfizer nor BioNTech shared detailed data from the clinical trial on the older children. They said they plan to submit the results to a scientific publication for peer review.
The Pfizer vaccine was the first cleared for emergency use on Dec. 11, less than a year after scientists began working on it. The Food and Drug Administration licensed it on Aug. 23, making it the only one of the three coronavirus vaccines in the country to win full approval. (The other two are from Cambridge-based Moderna and New Brunswick, N.J.-based Johnson & Johnson.)
Despite the speed with which the Pfizer vaccine was developed and tested, Barnett is confident it is safe in children ages 5 to 11 at the lower dose.
“Although it appears that the vaccine development process was fast, it was not because any corners are being cut,” she said. “It’s because everyone is working around the clock. And the safety of the doses being used for adults is very encouraging.”
Dr. Bill Gruber, a Pfizer senior vice president, told the Associated Press that his firm and BioNTech hope to apply to the FDA by the end of the month for emergency use in children ages 5 to 11, followed soon afterward with applications to European and British regulators.
Earlier this month, FDA chief Dr. Peter Marks said that once Pfizer turns over its study results, his agency would evaluate the data “hopefully in a matter of weeks.” Regulators at the Centers for Disease Control and Prevention would also have to sign off on the shots. Both agencies are guided by independent advisory panels of scientific experts who discuss the data at public hearings.
While children are at lower risk of severe illness or death from the coronavirus than adults, more than 5 million US children have tested positive for COVID-19 since the pandemic began and at least 460 have died, according to the American Academy of Pediatrics.
Cases in children rose dramatically as the Delta variant become the dominant strain. A small number of infected children have also developed a life-threatening condition called multisystem inflammatory syndrome in children, or MIS-C. Others may have symptoms that linger for months.
“I feel a great sense of urgency” in making the vaccine available to children under 12, Gruber told the AP. “There’s pent-up demand for parents to be able to have their children returned to a normal life.”
Federal regulators have to weigh the benefits of the vaccine against the risk of side effects. In rare cases, the mRNA vaccines of Pfizer and Moderna have led to myocarditis, an inflammation of the heart, in young people, particularly males, and most often after the second shot. Most of those patients responded well to medicine and rest and felt better quickly, said regulators. And a large Israeli study, based on electronic health records of 2 million people aged 16 and older, found that COVID-19 is far more likely than the vaccine to cause these heart problems.
While Pfizer hopes to expand the age groups that can receive its vaccine, it has also applied to regulators for permission to roll out a third shot to boost what it described as waning antibody levels in early recipients.
On Friday, an FDA advisory panel voted 16-2 to reject Pfizer’s request to offer the booster to anyone 16 and older at least six months after their second shot, saying that the firm had not proved it was necessary yet or that its benefits outweighed its risks. Instead, the panel, officially called the Vaccines and Related Biological Products Advisory Committee, voted unanimously to recommend offering it only to people 65 and older and those at high risk for severe COVID-19.
The FDA doesn’t have to follow the advice of its expert panels, but usually does. The agency is expected to announce its decision this week. An advisory panel to the CDC also plans to vote on who should be offered the booster and the timetable at a hearing on Wednesday and Thursday.
Anissa Gardizy of the Globe staff contributed to this report.