No cases of Covid-19 were seen in a trial involving 3,732 young volunteers who received two doses of the vaccine, compared to four cases in controls who had placebo injections.
Moderna says it will soon submit the data to regulators globally to seek approval for use in teens.
The Pfizer vaccine has already been approved for use in US adolescents.
Although teenagers rarely get seriously ill with Covid, they can spread the infection. Experts hope vaccinating them against the virus will help stop the pandemic.
The Pfizer-BioNTech vaccine, which is authorised for use in those aged over 16, is also being tested in children under 12, with the aim of involving babies from just six months old.
Moderna’s vaccine is currently authorised for people 18 and older.
The UK has approved three Covid vaccines for use in adults – Moderna, Oxford/AstraZeneca, Pfizer/BioNTech – but none yet for younger teens or children.