Moderna's Chief Medical Officer Discusses Vaccine for Children Under 6 Years Old

With COVID-19 cases dwindling, Americans have been letting down their guards after two years of the pandemic. But there's one group who can't relax quite yet: parents of children under 5 years old, who aren't eligible for vaccination. This might change soon, though, because Moderna released promising pediatric data from phase 2/3 of its KidCOVE study.

According to an announcement by the biotechnology company on March 23, 2022, a two-dose 25 microgram primary series of Moderna's COVID-19 vaccine (mRNA-1273) showed a "robust neutralizing antibody response" in children ages 6 months to 6 years old. The vaccine even had a "statistically significant" protection against the Omicron variant, though it was more effective against previous strains of COVID-19. Researchers reported minimal side effects and no red flags in children.

"We're really thrilled with the results" of the KidCOVE study, says Paul Burton, M.D., Ph.D., Moderna's Chief Medical Officer. "I think they show a very nice safety profile; the predictability and the effectiveness of antibodies is really reassuring."

Moderna is planning to request vaccine authorization for children ages 6 months to under 6 years of age from the U.S. Food and Drug Administration (FDA) and other global regulators. If all goes well, the vaccine could be available to younger children, optimistically, in late spring or early summer, says Dr. Burton.

"This is a huge priority for us. There's no other vaccine available" for these younger kids, says Dr. Burton, adding that experts are working around-the-clock to make it happen. "I think regulators and public health bodies also realize there's an unmet need here. They'll continue to do very thorough reviews, but as fast as they can."

In addition, Moderna announced it has applied for emergency use authorization of its COVID-19 vaccine for kids ages 6 to 11 years old. The drug manufacturer is also "updating our submission to the FDA for emergency use authorization of mRNA-1273 in adolescents ages 12 to 17 years with additional follow-up data," according to Stéphane Bancel, Chief Executive Officer of Moderna, in the March 23 statement.

Here's what parents need to know about the latest news.

Who Participated in Moderna's KidCOVE Study?

Moderna's KidCOVE study was divided into three age groups: 6 to under 12 years old, 2 to under 6 years old, and 6 months to under 2 years old. About 11,700 pediatric participants participated in these trials, and 6,700 were between 6 months to under 6 years old. According to Dr. Burton, approximately 5,000 got the vaccine and 2,000 received the placebo. "That's a rigorous, well-designed trial," he says.

Was the Vaccine Effective in Younger Kids?

In vaccinated younger kids, two doses of 25 micrograms provided "similar immunogenicity" to adults ages 18 to 25 years, who were given a 100 microgram two-dose vaccine.

"Vaccine efficacy in children 6 months to 2 years was 43.7 percent and vaccine efficacy was 37.5 percent in the 2 to under 6 years age group," according to the Moderna report. "The majority of cases were mild, and no severe COVID-19 disease was observed in either age group." This is great news for parents, because although the vaccine doesn't always protect against infection, it helps ward off severe illness and other complications. Also note that this data was reported during the Omicron wave.

Does It Protect Against Omicron?

Moderna developed its vaccine before the Omicron variant, so it's not made to fight against that particular strain of the coronavirus. That said, Omicron was predominant in the U.S. during this KidCOVE study, allowing experts could assess the effectiveness. The vaccine had "statistically significant, but lower efficacy" against Omicron, which is consistent with observational data from adults.

Why Do Children Receive a Lower Dose?

Kids ages 6 months to under 6 years will receive a 25 microgram two-dose primary series of the Moderna vaccine. Those ages 6 to under 12 years old get 50 micrograms. Adolescents and adults receive two doses of 100 micrograms each. What's the reason for the different doses?

"The way we looked at effectiveness is to measure antibody levels," says Dr. Burton. In younger kids, researchers determined that the smaller doses (25 micrograms) gave the perfect level of protection—comparable to the larger doses in adults. "We wanted to tailor the dose to the age group, and the size of the kids, to balance a great immune response with safety,'' says Dr. Burton.

What Were the Reported Side Effects?

According to the Moderna announcement, the "tolerability profile" of pediatric trial participants was "generally consistent" with that observed in older kids, adolescents, and adults. Most side effects were mild or moderate, and they included low-grade fever, injection site pain, and fatigue. These were most common after the second dose. "It's very predictable and exactly what we would expect," says Dr. Burton.

It's also important to note that no major red flags were reported in the KidCOVE study. Researchers didn't find any myocarditis or pericarditis (inflammation of the heart and its lining), multisystem inflammatory syndrome in children (MIS-C), or death.

Will Children Need a Boost Shot in the Future?

Currently, people ages 12 and up are recommended to get booster doses of the COVID-19 vaccine. Moderna is evaluating the need for a booster in children and adolescents, and Dr. Burton predicts one will probably be recommended in the future. We'll need to wait and see the specifics though.

"Up against Delta and the original virus, you do need some boosting, but you can probably extend that time period out. Up against Omicron, we really do need an Omicron-specific booster. We're working on that right now," says Dr. Burton. "You can boost with Spikevax (Moderna's FDA-approved COVID vaccine) but to get longevity of effect, we need an Omicron-specific booster because it's so different."

When Will Moderna Be Available to Older Children and Adolescents?

Currently, people ages 18 and up can receive Moderna in America. The manufacturer previously reported "positive topline data from the 6 to under 12 year old cohort, indicating a strong immune response one month after the second dose" according to their announcement. They've now initiated the submission process for FDA emergency use authorization, so hopefully, the vaccine will be available to American children ages 6 to 12 soon. Moderna is currently given to kids this age in Australia, Canada, and the European Union.

Additionally, Moderna it's updating its submission for FDA emergency use authorization for adolescents 12 and under 18 years old, who would receive a 100 microgram two-dose primary series. They've already gotten the go-ahead for vaccination in this age group for the "European Union, UK, Australia, Canada, Switzerland and other countries," says the Moderna statement.

Should Children Get Vaccinated When They Become Eligible?

Parents can make the decision themselves, but experts stress the importance of getting vaccinated when you're eligible. Moderna's vaccine "has been given to 550 million people around the world. There's really nothing we don't know about it in terms of its safety profile and how it behaves," says Dr. Burton. "People should not be nervous about this [mRNA] technology anymore. It's not something that's new and unstudied." Pfizer has also been proven safe and effective for everyone 5 and older.

But should you vaccinate your kids soon as they're eligible, or wait for the next COVID surge? "As a physician and a dad, I think the sensible, safe thing to do is get vaccinated now, assuming the vaccine is approved," says Dr. Burton. Afterwards, your kids should stay up-to-date with booster shots, which should be specifically formulated to new variants.

It's true that most kids get mild or asymptomatic cases of COVID-19, but severe illness has been reported on rare cases. Long COVID is also a concern for people of all ages. "We don't know what this virus is going to do to us 10 years from now," says Dr. Burton. What's more, unvaccinated kids have a higher likelihood of transmitting the virus to parents and caregivers, who might be at a greater risk for complications. For all of these reasons, experts stress that the benefits of vaccination outweigh the risk.

Talk to your health care provider for more information about the vaccines.