(CNN) – In a phase 2/3 trial of 3,732 children ages 12 to 17 in the United States, blood tests showed that Moderna’s covid-19 vaccine produced an immune response that was equivalent to previous findings in adults.

The company did not provide a percentage of efficacy, as the trial was not designed to specifically examine that parameter.

However, initial observations found that none of the children who received the vaccine became ill with COVID-19 starting 14 days after their second dose.

Four of the children who received the placebo tested positive for COVID-19, which Moderna says is “consistent with 100% vaccine efficacy.” The company notes that the figure could change as more data is collected.