(Adds background on safety concerns, data) Nov 9 (Reuters) - Moderna Inc on Tuesday applied for European authorization of its COVID-19 vaccine in children aged 6-11 years, weeks after it delayed a similar filing with U.S. regulators. The European Union had in July authorised the vaccine for use in teens aged 12 to 17 years, but several countries including Sweden paused its use for people aged 30 and younger due to rare heart-related side-effects. Moderna said in late October the U.S. drugs regulator needed more time to complete its review for use in the 12-17 age group as it studies the risk of a type of heart inflammation called myocarditis after vaccination. The drugmaker delayed the U.S. application for children aged 6 to 11, while the FDA completes its review for the vaccine's use in the 12-17 age group.