Will babies and young kids get COVID-19 vaccines before a BA.2 surge? Here's what health experts say. - USA TODAY

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After enduring months of confusion and multiple setbacks, parents of young children were elated to find out Moderna plans to request the Food and Drug Administration to authorize a COVID-19 vaccine for kids under 6. 

Although parents welcomed the much-anticipated news, the BA.2 strain of the omicron variant continues to gain ground in the U.S., and access to these life-saving vaccines for 18 million of the nation's youngest is still weeks away.

Pfizer-BioNTech, which also plans to request FDA authorization for its COVID vaccine for children under 5, expects its extended clinical trial to be completed by early April. Their vaccine could get the green light as early as the end of that month, said Dr. Anna Durbin, professor and director of the Center for Immunization Research at Johns Hopkins Bloomberg School of Public Health.

Moderna says it expects to get its FDA authorization  by early summer.

That means young children may not be able to their shots before BA.2 becomes the dominant variant in the U.S. – which could happen as soon as next week. But health experts are hopeful they'll get access before the variant causes another surge in cases.

It's going to be a tight race, said Dr. David Wohl, a professor of medicine at the University of North Carolina's division of infectious diseases. 

"Vaccinating children is really key," he said. "All the ingredients are there to see an uptick starting in very young people, and so that's what we have to pay attention to."

While overall cases in the U.S. have been falling recently, there is concern as BA.2 is causing increases in other nations.

The BA.2 version of omicron arrived in the U.S. late last year and has been steadily spreading, now accounting for more than a third of cases here, according to the Centers for Disease Control and Prevention. As a percentage of cases, BA.2 has roughly doubled each week for the last month.

At the same time, the sharp decrease in cases following the winter omicron surge is beginning to plateau. CDC director Dr. Rochelle Walensky told reporters in a White House briefing Wednesday the agency is recording small increases in the Northeast.

"We're seeing a modest uptick of sites reporting an increase of virus levels in wastewater in some communities," she said. "Sustained trends over time can give us an early indication of COVID-19 infections in communities, so these are the areas that we are watching carefully."

Rising cases due to BA.2 in at least a dozen Asian and European countries may predict what's in store for the U.S. in the upcoming weeks, experts say. The United Kingdom, which has been a leading indicator of cases in the U.S., has seen a significant surge. 

"That indicates that maybe the virus is getting a foothold, but it's a little hard to tell right now," said Jeffrey Shaman, director of the Climate and Health Program at the Columbia University Mailman School of Public Health. "Because the U.K. is ahead of us on this, it provides sort of an analogy that we can work from."

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BA.2 doesn't appear to cause more severe illness or evade immunity but may be up to 60% more transmissible than the original omicron variant, said Amber D'Souza, professor at the Johns Hopkins Bloomberg School of Public Health. 

"Initial data suggested BA.2 has a reproductive rate, or R-naught, around 8 to 12," she said. "This is a high reproductive rate, similar to that of chicken pox, meaning each infected person infects many other people."

Previous studies estimated the R-naught of the original omicron variant between 7 and 10. 

Will the COVID vaccine work for kids?

U.S. health officials continue to urge Americans to get vaccinated to protect themselves against infection and prevent community spread. But while COVID-19 vaccines were developed with unprecedented speed for adults, it's taken at least twice as long for shots to be available for young children, who are at far less risk from serious illness.

Children represent only 19% of all infections and up to 1.5% of all COVID-19 hospitalizations since the pandemic began, according to the American Academy of Pediatrics, but it continues to be one of their leading causes of death. The CDC reported more than 400 kids under 5 have died of COVID-19, many in the past few months.

Data released Wednesday by Moderna showed two-doses of its 25 microgram vaccine is safe and effective in kids ages 6 months to 6 years. Pfizer is testing smaller doses for children under 5, but had to add a third shot to its study when two injections didn't prove strong enough.

Although both of the vaccine makers' studies were conducted during the initial omicron wave, there's no reason to think their vaccines won't be effective against BA.2, said Stephen Kissler, research fellow in the Department of Immunology and Infectious Diseases at Harvard T.H. Chan School of Public Health. 

He said BA.1 and BA.2 "interact with the human immune system in pretty similar ways."

"My expectation is that even though the vaccine trials were done for the major omicron wave in the U.S., we should see pretty similar results for BA.2," Kissler said.

The Biden administration already has secured enough vaccine for children under 6, White House COVID-19 Response Coordinator Jeff Zients said during Wednesday's briefing.  

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"We will be ready operationally … when the vaccine is authorized and recommended," he said. "We'll have those vaccinations available in tens of thousands of locations across the country that people know and trust."

In Moderna's study of 6,700 kids, researchers found the vaccine was 43.7% effective in children 6 months to 2 years, and 37.5% in kids 2 to 6 years. It's a far cry from the 95% efficacy rate first reported in adults against the original coronavirus, but health experts say it's better than nothing – for now.

After young children get the primary series, Wohl said, Moderna will likely look at data for a booster shot to increase their protection against these variants.

"We do that kind of boost for many different diseases with vaccinations," he said. "Clearly we're seeing that there's a lot of work to do to figure out what's the right dose that gets you the type of response that you want in littler kids."

But the priority is getting initial shots to children before BA.2 causes a spike in cases or the U.S. experiences another summer surge. As parents wait, health experts say they can protect their little ones by making sure those around them are vaccinated and boosted.

"Remember, children get it from us," Wohl said. "The best way to protect a child is not only by vaccinating them but not having them to be exposed to the virus in the first place."

Contributing: Karen Weintraub, USA TODAY. Follow Adrianna Rodriguez on Twitter: @AdriannaUSAT. 

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