Moderna said Wednesday its Covid-19 vaccine generated a strong immune response and was generally well-tolerated in kids ages 6 months up to 6 years.
The drugmaker said two 25-microgram doses of the vaccine, a quarter of the dose given to those 18 and older, produced an antibody response similar to what was seen in a clinical trial of adults.
For the approximately 6,900 children in the trials, the majority of side effects were "mild or moderate," and no cases of a rare heart condition called myocarditis were reported, the company said.
Protection against infection from the omicron variant of the coronavirus was low. For children ages 6 months to 2 years, efficacy was 43.7 percent, and in children ages 2 to 6, it was only 37.5 percent. Moderna said the majority of the infections were mild. There were no cases of severe illness, hospitalization or death.
The findings may come as welcome news to some parents. A recent report from the Centers for Disease Control and Prevention found that during the surge of the omicron variant, which began in late December, the hospitalization rate for infants and children up to age 4 was about five times the rate during the peak of the delta variant last summer and fall.
Moderna's vaccine should reduce the risk of hospitalization or serious illness in kids, even if it doesn't stop infection, said Dr. Isaac Bogoch, an infectious disease specialist at the University of Toronto.
Young kids "can still have severe outcomes, although it is much less frequent compared to older cohorts," he said.
Moderna said it plans to submit the data to the Food and Drug Administration and other regulators in the coming weeks.
It's hard to predict what action the FDA will take, given the lower efficacy, said infectious diseases expert Dr. Jesse Goodman of Georgetown University, former FDA chief scientist.
"FDA could decide the data are sufficient for emergency authorization given that there is not another vaccine available at present for this age group," he said. "However, kids this age, if otherwise healthy and without other medical issues, are usually at low risk of complications of Covid so how widely the vaccine would be used or recommended is unclear."
Most children in the age group are ineligible to receive a Covid vaccine; the Pfizer-BioNTech vaccine has been authorized for use in the U.S. for people as young as 5. Moderna’s vaccine has been authorized only for adults.
Will parents bother getting their kids the vaccine? John Moore, a professor of microbiology and immunology at the Weill Cornell Medical College, said: "Some might. Some."
Bogoch agreed, saying uptake of the vaccine in this age group may be "moderate," given kids are less likely to get severely ill.
Pfizer said last month that it was postponing its rolling application to the FDA to expand the use of its vaccine for kids under 5 after it found that two doses of its shot didn’t generate a strong enough immune response in kids ages 2 to 4.
The Pfizer vaccine dose for young kids is 3 micrograms, lower than the 25 micrograms Moderna tested for the age group.
Pfizer said at the time that it would wait for its data on a three-dose series of the vaccine, because it believes three doses “may provide a higher level of protection."
While Moderna is asking the FDA to authorize two doses of its vaccine for kids under 6, the company said Wednesday it is preparing to evaluate the potential of a booster dose for all children.
Goodman of Georgetown University said a third shot, or booster dose, may enhance the protection provided by the Moderna vaccine.
He said it's unclear if the protection of the first two doses will drop off further with time, as has been seen in adults who received the primary series.