Only kids 12 and older are eligible — so far — to get vaccinated against COVID-19 in the U.S. But the shots could be available for younger children as soon as this fall, say researchers studying the vaccine in that age group.

Only kids 12 and older are eligible — so far — to get vaccinated against COVID-19 in the U.S. But the shots could be available for younger children as soon as this fall, say researchers studying the vaccine in that age group. / AP

With the U.S. in the grips of a frightening surge of coronavirus cases, many parents are understandably eager to know when the COVID-19 vaccine will finally be available for children under 12.

This age group accounts for about 50 million Americans and currently none of them qualify for a shot. But scientists are racing to figure out how one of the COVID-19 vaccines currently available for adults could be given to this age group.

Pfizer and Moderna are both running large pediatric trials to study the effectiveness and safety of using their COVID-19 mRNA vaccines for children under 12.

Here's what we can expect:

What do we know from the vaccine studies of children under 12?

Researchers have already shared some early findings about how a COVID-19 vaccine may be used in younger children.

In the clinical trial for the Pfizer vaccine, the data collected shows that one-third of the adult dose is the optimal range for children younger than 12 and older than 5, says Dr. Flor Muñoz at Texas Children's Hospital and Baylor College of Medicine, who is running the Pfizer study.

" 'Optimal' meaning the dose that will give you a similar immune response that will be protective, as we have seen with adolescents, with the minimum amount of side effects," she says.

Muñoz and her team have enrolled children as young as 6 months and up through age 11. Her team is now in the next phase of the study, where they randomly assign children either to receive a vaccine or a placebo. Comparing a vaccinated group with a placebo group allows researchers to be confident that any benefit or risk during the study is truly related to the vaccine.

The Pfizer study won't test to see whether the vaccine actually prevents children from getting sick. Instead, it will look at their blood to see if they are making the kinds of antibodies that have been shown to prevent disease. Studies of the Pfizer COVID-19 vaccine in adults have already shown that such antibodies indicate that someone is well-protected from becoming severely ill with COVID-19. Children will remain part of the study for two years so researchers can determine how long protection lasts, whether any rare, long-term health issues arise, and whether a booster is needed.

Moderna is conducting a similar pediatric study of its COVID-19 vaccine. Children enrolling in the Moderna trial now have a 3 to 1 chance of getting the vaccine, because only 25% of the participants are in the placebo arm of the trial.

"We are testing different doses in the different age groups because younger children may not need the same dose as adults," says Dr. Jacqueline Miller, senior vice president at Moderna.

When could shots be available?

This depends on how quickly the studies collect the necessary data and what regulators at the Food and Drug Administration ultimately decide when they review the results.

At the moment, it looks like the Pfizer vaccine will be the first shot available to children under 12. The vaccine-maker expects to have enough data by the end of September to support an emergency use authorization for its vaccine in children who are ages 5 to 11.

"We're hoping to have authorization — depending on both results and, of course, a few decisions — not too long after the school year starts," Dr. Phil Dormitzer, chief scientific officer for viral vaccines at Pfizer, told NPR recently.

The data for children under 5 will be submitted shortly thereafter, a Pfizer spokesperson told NPR.

Right now the other mRNA COVID-19 vaccine authorized for use in the U.S. — Moderna's — can be given to individuals who are 18 and older. Moderna says it expects to have enough data by the end of the year to seek authorization for a shot that can be given to children who are between the ages of 6 and 11.

Moderna recently expanded the size of its trial and is now enrolling 12,000 children in an effort to increase the likelihood of detecting any rare, but serious adverse events. The Pfizer study currently plans to enroll up to 4,500 children, a company spokesperson told NPR.

"The safety profile so far is really comparable to the adults and, so far, no safety concerns," says Miller, referring to the Moderna vaccine. Data for children under 6 could be submitted to the FDA by "early next year," she says, "but that could be done more rapidly, depending on the rate of enrollment."

Do we need to give children COVID-19 shots?

Even with the emergence of new variants, the risk of severe illness from COVID-19 remains quite low for younger children compared to the adult population. But with so many infections each day in the U.S., a huge number of children are now being exposed to the virus and testing positive.

More than 120,000 COVID-19 cases were reported among children between Aug. 5 and 12 — about 18% of the total weekly case count, according to the American Academy of Pediatrics.

"They do have a milder illness and lower likelihood of becoming infected," says Muñoz of Texas Children's Hospital. "But they can be infected. They can have severe illness and they can transmit the virus."

And with such high numbers of infections nationally and no protection from a vaccine if they do get infected, more children are at risk of becoming one of the unlucky few who do get seriously ill or face long-term symptoms post-infection — a syndrome widely known as "long COVID."

Dr. Paul Offit, a pediatric vaccine specialist at Children's Hospital of Philadelphia, says a vaccine for younger children can't come soon enough, given the growth in cases.

Only adding to the sense of urgency, hospitals in some parts of the country are admitting record numbers of children with COVID-19.

"We have more pediatric patients right now hospitalized with COVID than at any point prior in this pandemic," says Dr. LouAnn Woodward, who oversees the University of Mississippi Medical Center. "We are seeing a younger group of patients that are getting very sick with this."

In a letter sent earlier this month, the head of the AAP urged the FDA to work "aggressively toward authorizing safe and effective COVID-19 vaccines for children under age 12 as soon as possible."

"Simply stated, the delta variant has created a new and pressing risk to children and adolescents across this country, as it has also done for unvaccinated adults," wrote AAP president Dr. Lee Savio Beers.

Many parents do not want to risk their children's health, especially as the school year begins — a fact that's also reflected in the outpouring of interest from parents who are trying to enroll their kids in the clinical trials.

"I get multiple emails a day asking, and unfortunately we just have limited spots," says Baylor College of Medicine's Dr. Erin Nicholson, who is running a study of the Moderna vaccine in children under 12.

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