The Food and Drug Administration has paved the way for children ages 5 to 11 to get Pfizer's Covid-19 vaccine.
The FDA has cleared kid-size doses — just a third of the amount given to teens and adults — for emergency use, and up to 28 million more American children could be eligible for vaccinations as early as next week.
One more regulatory hurdle remains: On Tuesday, advisers to the Centres for Disease Control and Prevention will make more detailed recommendations on which youngsters should get vaccinated, with a final decision by the agency's director expected shortly afterwards.
"With this vaccine kids can go back to something that's better than being locked at home on remote schooling, not being able to see their friends," said Dr Kawsar Talaat, of Johns Hopkins University. "The vaccine will protect them and also protect our communities."
A few countries have begun using other Covid-19 vaccines in children under 12, including China, which just began vaccinations for 3-year-olds. But many that use the vaccine made by Pfizer and its partner BioNTech are watching the US decision, and European regulators just began considering the companies' kid-size doses.
With FDA's action, Pfizer plans to begin shipping millions of vials of the paediatric vaccine — in orange caps to avoid mix-ups with the purple-capped doses for everyone else — to doctors' offices, pharmacies and other vaccination sites. Kids will get two shots, three weeks apart.
While children are at lower risk of severe illness or death from Covid-19 than older people, 5- to 11-year-olds still have been seriously affected - including more than 8300 hospitalisations, about a third requiring intensive care, and nearly 100 deaths since the start of the coronavirus pandemic, according to the FDA.
And with the extra-contagious Delta variant circulating, the government has counted more than 2000 coronavirus-related school closings just since the start of the school year, affecting more than a million children.
Earlier this week, the FDA's independent scientific advisers voted that the paediatric vaccine's promised benefits outweigh any risks. But several panellists said not all youngsters would need to be vaccinated, and they preferred the shots be targeted to those at higher risk from the virus.
Nearly 70 per cent of 5- to 11-year-olds hospitalised for Covid-19 in the US have other serious medical conditions, including asthma and obesity, according to federal tracking. Additionally, more than two-thirds of youngsters hospitalised are Black or Hispanic, mirroring long-standing disparities in the disease's impact.
The question of how broadly Pfizer's vaccine should be used will be a key consideration for the CDC and its advisers, who set formal recommendations for paediatricians and other medical professionals.
A Pfizer study of 2268 schoolchildren found the vaccine was nearly 91 per cent effective at preventing symptomatic Covid-19 infections, based on 16 cases of Covid-19 among kids given dummy shots compared to just three who got vaccinated.
The kid dosage also proved safe, with similar or fewer temporary reactions — such as sore arms, fever or achiness — that teens experience.
But the study wasn't large enough to detect any extremely rare side effects, such as the heart inflammation that occasionally occurs after the second full-strength dose, mostly in young men and teen boys. It's unclear if younger children getting a smaller dose also will face that rare risk.
Some parents are expected to vaccinate their children ahead of family holiday gatherings and the winter cold season.
But a recent Kaiser Family Foundation survey suggests most parents won't rush to get the shots. About 25 per cent of parents polled earlier this month said they would get their children vaccinated "right away". But the remaining majority of parents were roughly split between those who said they will to wait to see how the vaccine performs and those who said they "definitely" won't have their children vaccinated.
The similarly made Moderna vaccine also is being studied in young children, and both Pfizer and Moderna are also testing shots for babies and preschoolers.