In a Phase 2-3 study in 3,732 children aged 12 to 17 years in the United States, blood tests showed that the vaccine produced an immune response consistent with previous results in adults.
The study was not designed to specifically test efficacy. However, initial observations showed that none of the children who received the vaccine developed Covid-19 14 days after the second dose. Four of the children who received the placebo tested positive for Covid-19, representing 100% efficacy of the vaccine, according to Moderna. The company notes that this number may change as more data is collected.
In the study, a case was defined as someone who had at least two symptoms of coronavirus or one symptom and a positive Covid-19 test.
The company also looked at how well the vaccine worked after a single dose. The results indicate that after one dose, the vaccine was 93% effective in preventing mild cases of Covid-19 who had only one symptom of coronavirus disease and not two or more symptoms.
The Moderna vaccine is already approved for use in people aged 18 years and older. Now that Moderna has submitted an application to the FDA for emergency approval of the vaccine for adults, the agency will review the data submitted by the company and consult with its advisors as appropriate. If the data is reliable, the FDA will give the go-ahead to use the vaccine in young people.