With federal regulators set to decide whether or not they plan to authorize COVID vaccines for kids under the age 5 this week, when might parents expect shots to begin?
Parents have been pressing federal officials for months for the opportunity to protect their smallest children as more adults shed masks and abandon other public health precautions.
The nation’s 18 million children under 5 are the only age group not yet eligible for vaccination.
While the race is on to get the youngest members of the population vaccinated, which vaccine will work best and when might one be approved?
Here's what we know so far.
Which vaccines are seeking approval for children under 5 and where do they stand?
The Food and Drug Administration's outside panel of advisers will meet on June 14-15 to evaluate both Pfizer's and Moderna's shots for younger kids.
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Moderna has asked U.S. regulators to authorize low doses of its COVID-19 vaccine for children younger than 6.
Moderna submitted data to the Food and Drug Administration in April that it hopes will prove two low-dose shots can protect babies, toddlers and preschoolers -- albeit not as effectively during the omicron surge as earlier in the pandemic.
“There is an important unmet medical need here with these youngest kids,” Dr. Paul Burton, Moderna's chief medical officer, told The Associated Press. Two kid-size shots “will safely protect them. I think it is likely that over time they will need additional doses. But we're working on that.”
Currently, Pfizer's COVID vaccine has been the only one approved for emergency use in the US for children between the ages of 5 and 17.
The vaccine competitor also recently announced three doses of its COVID-19 vaccine offer strong protection for children younger than 5.
Pfizer has had a bumpier time figuring out its approach. It aims to give tots an even lower dose — just one-tenth of the amount adults receive — but discovered during its trial that two shots didn’t seem quite strong enough for preschoolers. So researchers gave a third shot to more than 1,600 youngsters — from age 6 months to 4 years — during the winter surge of the omicron variant.
In a press release, Pfizer and its partner BioNTech said the extra shot did the trick, revving up tots’ levels of virus-fighting antibodies enough to meet FDA criteria for emergency use of the vaccine with no safety problems.
What still needs to happen before shots can begin and when are they expected?
On Wednesday, the FDA will ask an independent panel of vaccine experts to debate both companies’ data before voting. The FDA is not required to follow the group’s recommendations, but the process is seen as a key step in publicly vetting the shots.
The FDA is expected to make its official decision shortly after Wednesday’s all-day meeting. The next step: the Centers for Disease Control and Prevention, which recommends how to use vaccines, will convene its own expert panel to debate which tots need vaccinations.
Chicago Department of Public Health Commissioner Dr. Allison Arwady said she expects the FDA could could clear the way for shots to begin this summer.
"My guess right now is it will be June when we will have potentially vaccine available for those youngest children," she said during a Facebook Live. "But it all depends on the FDA and the CDC and its external experts advising."
If regulators clear the shots by one or both companies, vaccinations could begin as soon as next week with the drugmakers ready to rapidly ship doses ordered by the government.
The Biden administration said this month that children under 5 may be able to get their first COVID-19 vaccination doses as soon as June 21, if federal regulators authorize shots for the age group, as expected.
White House COVID-19 coordinator Ashish Jha said shipments to doctors' offices and pediatric care facilities would begin soon after FDA authorization, with the first shots possible the following week.
Jha said states can begin placing orders for pediatric vaccines on Friday, and said the administration has an initial supply of 10 million doses available. He said it may take a few days for the vaccines to arrive across the country and vaccine appointments to be widespread.
How effective are the vaccines in children?
Whether it’s one company’s shots or both, FDA vaccine chief Dr. Peter Marks said the agency will “move quickly without sacrificing our standards” in deciding if tot-sized doses are safe and effective.
“It’s critically important that we have the proper evaluation so that parents will have trust in any vaccines that we authorize,” Marks told a Senate committee.
Earlier this year, the FDA, worried about the omicron variant's toll on kids, had taken the extraordinary step of urging Pfizer to apply for OK of the extra-low dose vaccine before it's clear if tots will need two shots or three. The agency's plan could have allowed vaccinations to begin within weeks.
But in February, the FDA reversed course and said it had become clear the agency needed to wait for data on how well a third shot works for the youngest age group. Pfizer said in a statement at the time that it expected the data by early April.
Marks said he hoped parents would understand that the agency's decision was part of its careful scientific review of the evidence Pfizer has submitted so far.
That information "made us realize that we needed to see data from a third dose from the ongoing trial in order to make a determination," Marks told reporters. “We take our responsibility for reviewing these vaccines very seriously because we’re parents as well."
In a study of kids ages 6 months through 5 years, two Moderna shots — each a quarter of the regular dose — triggered high levels of virus-fighting antibodies, the same amount proven to protect young adults, Burton said. There were no serious side effects, and the shots triggered fewer fevers than other routine vaccinations.
But the vaccine proved between about 40% and 50% effective at preventing symptomatic COVID-19 during the trial. Burton blamed the omicron variant's ability to partially evade vaccine immunity, noting that unboosted adults showed similarly less effectiveness against milder omicron infections. While no children became severely ill during the study, he said high antibody levels are a proxy for protection against more serious illness — and the company will test a child booster dose.
COVID-19 vaccines aren't as effective against the super-contagious omicron mutant — in people of any age — and Moderna's study found the same trend.
At the same time, preliminary data suggested Pfizer and its partner BioNTech's three-dose series is 80% effective in preventing symptomatic COVID-19, the companies said, but they cautioned the calculation is based on just 10 cases diagnosed among study participants by the end of April. The study rules state that at least 21 cases are needed to formally determine effectiveness, and Pfizer promised an update as soon as more data is available.
“The study suggests that a low, 3-microgram dose of our vaccine, carefully selected based on tolerability data, provides young children with a high level of protection against the recent COVID-19 strains,” he said in a statement.
Federal health officials said Sunday that kid-sized doses of Pfizer’s COVID-19 vaccines appear to be safe and effective for kids under 5. Late last week the FDA posted a similar analysis of Moderna’s shots for children under 6.
The FDA said children who received Pfizer’s shots during testing developed high levels of virus-fighting antibodies expected to protect them against coronavirus. That’s the basic threshold needed to win FDA authorization. But additional testing turned up key differences, with stronger results for Pfizer.
Why do health officials want to get children vaccinated?
While only about 3% of U.S. COVID cases are in the age group 6 months to 4 years, hospitalization and death rates in that group are higher than those for older children, according to the FDA’s analysis — one reason experts have said protecting this group is important.
It’s not clear how much demand there will initially be for the shots. A recent survey suggests only 1 in 5 parents of young children would get their kids vaccinated right away. Vaccines have been available since November for older U.S. schoolchildren, yet less than a third of those ages 5 to 11 have gotten the two recommended doses, according to government figures.
Would children be given the same size dose as adults?
For the youngest children, each company is offering different dose sizes and number of shots, beginning at 6 months through 4 years for Pfizer and through 5 years for Moderna.
Pfizer and its partner BioNTech plan to offer two shots three weeks apart followed by a third at least two months later — each one-tenth the dose given to adults. Pfizer is currently the only company with a COVID-19 vaccine for older U.S. children.
Moderna is seeking FDA clearance for two shots, each a quarter of its adult dose, given about four weeks apart.
The FDA currently allows Moderna’s vaccine to be used only in adults. But some countries allow full-size doses for teens and half-size shots for kids ages 6 to 11 — a step the FDA also is considering.
What about side effects?
Parents may find it confusing that Moderna is seeking to vaccinate the youngest children before it's cleared to vaccinate teens. While other countries already have allowed Moderna’s shots to be used in children as young as 6, the U.S. has limited its vaccine to adults.
The FDA hasn't ruled on Moderna's earlier request to expand its shots to 12- to 17-year-olds because of concern about a very rare side effect, heart inflammation.
Heart inflammation sometimes occurs in teens and young adults, mostly males, after receiving either the Pfizer or Moderna vaccines. Moderna is getting extra scrutiny because its shots are a far higher dose than Pfizer’s.
But the CDC recently found the risk of myocarditis and other inflammatory syndromes was higher following infection from COVID than after Pfizer or Moderna vaccination in males and females ages 5 and older.
The company said that, armed with additional evidence, it is updating its FDA application for teen shots and requesting a green light for 6- to 11-year-olds, too. Dr. Stephen Hoge, Moderna’s president, said he’s optimistic the company will be able to offer its vaccine “across all age groups in the United States by the summer.”
Moderna says its original adult dose — two 100-microgram shots — is safe and effective in 12- to 17-year-olds. For elementary school-age kids, it’s using half the adult dose.
About 1.5 million adolescents have used the Moderna vaccine in other countries, “and so far we've seen very reassuring safety from that experience," Hoge said.
The heart risk also seems linked to puberty, and regulators in Canada, Europe and elsewhere recently expanded Moderna vaccinations to kids as young as 6.
“That concern has not been seen in the younger children,” said Northwestern’s Muller.
While the study wasn't large enough to detect very rare side effects, Moderna said the small doses were safe and that mild fevers, like those associated with other common pediatric vaccines, were the main reaction.