(Reuters) — Moderna Inc has begun dosing patients in a mid-to-late stage study of its COVID-19 vaccine, mRNA-1273, in children ages 6 months to less than 12 years, the company said on Tuesday.

The study will assess the safety and effectiveness of two doses of mRNA-1273 given 28 days apart and intends to enroll about 6,750 children in the United States and Canada.

The vaccine has already been authorized for emergency use in Americans who are aged 18 and older.

In a separate study which began in December, Moderna is also testing mRNA-1273 in adolescents between 12 and 18 years old.

The latest study is being conducted in collaboration with the National Institute of Allergy and Infectious Diseases (NIAID) and the Biomedical Advanced Research and Development Authority (BARDA).