Moderna Inc said on Thursday it has filed for US authorization to use its COVID-19 vaccine in adolescents aged 12 to 18, the latest company to seek approval to help expand the inoculation drive in the country.

Moderna's vaccine is already being used in the United States, the European Union and Canada for anyone over 18. The drugmaker has already submitted applications to the European and Canadian health regulators seeking authorization for the vaccine's use in adolescents.

Moderna's two-shot vaccine last month was shown to be effective in adolescents aged 12-17 and showed no new or major safety problems in a clinical trial which evaluated the vaccine in 3,732 teenagers.

Vaccinating children has been considered key to achieving "herd immunity" and the US has already authorized Pfizer and German partner BioNTech SE's COVID-19 vaccine for use in children as young as 12.