WASHINGTON — Federal regulators broadened access to updated coronavirus booster shots on Wednesday to include children as young as 5, hoping to bolster protection against the now-dominant version of the Omicron variant that accounts for a vast majority of cases in the United States.
The revised shot developed by Pfizer-BioNTech previously had been cleared for those 12 and older, while Moderna’s updated booster was available to those 18 and older. The action by the Food and Drug Administration expands eligibility for Pfizer’s shot to children as young as 5 and makes available Moderna’s shot to children 6 and older.
“Since children have gone back to school in person and people are resuming prepandemic behaviors and activities, there is the potential for increased risk of exposure to the virus,” said Dr. Peter Marks, the agency’s top vaccine regulator. While Covid-19 is typically less severe in children than adults, he said, “more children have gotten sick with the disease and have been hospitalized” as the pandemic has progressed.
Dr. Rochelle P. Walensky, the director of the Centers for Disease Control and Prevention, quickly signed off on the new booster shots, the final step to making them available to young children around the country.
Moderna’s updated shots will be available for children at 34,000 sites, including pharmacies and pediatricians’ offices, according to a senior Biden administration official. More than nine out of 10 Americans are within five miles of a dose, the official said. Children ages 12 to 17 will be given the adult dosage of Moderna’s shot, while those 6 to 11 will be given a half dose.
Because Pfizer’s updated booster for children requires a different vial, it is not expected to become available until next week. Both companies’ boosters are authorized for administration at least two months after a child has completed the initial two-shot series or received a booster dose.
While vaccination continues to be the linchpin of the Biden administration’s strategy to combat the pandemic, each successive shot has drawn fewer takers. Close to half of the 226 million Americans who completed the initial round of vaccination received at least one booster shot before the new ones were authorized for older age groups at the end of August.
But as of last weekend, only 13 million to 15 million people had received an updated booster shot, Dr. Ashish K. Jha, the White House Covid-19 coordinator, estimated on Tuesday.
No new booster shots have been cleared yet for children under 5. Pfizer and Moderna are expected to have results later this year from studies examining the new shots in the youngest children.
Many families appear to have already decided against vaccinating their children against the coronavirus. Only about a third of children ages 5 to 11 have completed an initial round of vaccination, according to C.D.C. data. Of those children, only about 16 percent went on to receive the original booster shot, which was cleared for that age group in May.
The redesigned boosters target BA.4 and BA.5, both subvariants of Omicron. Since Omicron first emerged in the United States nearly a year ago, the variant and its descendants have dominated the Covid landscape, with BA.5 still accounting for roughly 80 percent of cases in the United States.
The authorization of the new shots on Wednesday was especially significant because so few children have been boosted, said Dr. Yvonne Maldonado, a pediatric infectious disease physician who led Pfizer’s pediatric Covid-19 vaccine trials at Stanford Medicine.
Covid-19 remains a major cause of death among children, Dr. Maldonado said, adding that vaccination can provide more durable protection than prior infection.
