Moderna says its low-dose COVID vaccine generates immune response in kids

Moderna says its clinical trials with children aged six to 11 showed two doses that were half the size of its adult shots produced similar levels of virus-fighting antibodies in children.

Announcement comes as rival Pfizer awaits approval for its pediatric vaccine in both U.S. and Canada

A 15-year-old poses for a photo after getting his first dose of the Pfizer COVID-19 vaccine earlier this year in Freeport, N.Y. As Pfizer waits to hear if its vaccine for younger children will be approved, Moderna announced Monday that its lower-dose vaccine for kids six- to 11-year-olds is safe and generates an antibody response. (Mary Altaffer/Associated Press)

Moderna said Monday that a low dose of its COVID-19 vaccine is safe and generates an immune response in six- to 11-year-olds as the manufacturer joins its rival Pfizer in moving toward expanding shots to children.

Pfizer-BioNTech's kid-size COVID-19 vaccine doses are closer to widespread use. They are undergoing evaluation by the U.S. Food and Drug Administration (FDA) for children in nearly the same age group, five to 11, and could be available in the U.S. by early November. It is also awaiting approval from Health Canada for use in vaccinating Canadian kids. 

Pfizer's vaccine is already authorized for anyone 12 or older in both the U.S. and in Canada. 

Both Pfizer and Moderna have been studying lower doses for younger children. 

Researchers tested two Moderna shots for the six- to 11-year-olds, given a month apart, that each contained half the dose given to adults.

Children in study developed antibodies

Preliminary results showed vaccinated children developed virus-fighting antibodies similar to levels that young adults produce after full-strength shots, Moderna said in a news release on Monday. 

The study involved 4,753 children aged six to 11 who got either the vaccine or dummy shots. Moderna said that like adults, the vaccinated youngsters had temporary side effects including fatigue, headache, fever and injection site pain.

The study was too small to spot any extremely rare side effects, such as myocarditis (heart inflammation) that has occurred in a small number of cases after either Moderna or Pfizer shots — which are both mRNA vaccines — mostly among young men.

WATCH | Cardiologist says risk of myocarditis is likely low in Pfizer-BioNTech kids vaccine:

Myocarditis risk from Pfizer vaccine appears low in kids, says specialist

2 years ago
Duration 4:17
A review of data suggests the Pfizer-BioNTech COVID-19 poses a very low risk of heart inflammation in children, says cardiologist Christopher Labos. Pfizer is seeking approval of its vaccine for ages five to 11 in the U.S. (Esteban Felix/The Associated Press)

Moderna released no further details and hasn't submitted its data to a scientific journal but said it plans to share the interim results with the FDA and global regulators soon.

Due to the small size of the ongoing study, the company cannot calculate the vaccine's effectiveness in actually preventing infections in children unless there are sufficient COVID-19 cases within the subjects to compare rates between vaccinated and unvaccinated participants.

The FDA hasn't yet ruled on the company's application to expand its vaccinations to 12- to 17-year-olds in the U.S., although some countries, including Canada, have cleared Moderna's shots for adolescents.

U.S. may begin child vaccinations in November

But the U.S. is expected to begin vaccinating children under 12 sometime next month, if the FDA clears low doses of the Pfizer vaccine for five- to 11-year-olds. 

Pfizer reported last week that its kid-size doses proved nearly 91 per cent effective at preventing symptomatic COVID-19 in that age group, even as the extra-contagious delta variant was spreading widely.

FDA advisers will weigh Pfizer's evidence in a public meeting Tuesday. If the agency authorizes Pfizer's kid shots, the Centers for Disease Control and Prevention is set to recommend who should receive them by the following week. 

With files from CBC News

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