Moderna is set to begin testing its coronavirus vaccine on thousands of children as young as 12.
The US drugmaker will hold trials in Idaho, Minnesota, New York, Oklahoma, Texas and Utah, according to a post by the firm on clinicaltrials.gov.
Three thousand volunteers between the ages of 12 and 18 are to be given two jabs, four weeks apart, with half receiving placebos - though the company said it is "not yet recruiting".
Federal officials said it is crucial the vaccine is tested on children prior to widespread distribution next year.
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The Moderna vaccine, which final testing showed had over 94 per cent efficacy, is expected to be approved for emergency use in the UK by the Medicines and Healthcare products Regulatory Agency in the next couple of weeks.
Pfizer/BioNTech - which has 97 per cent effectiveness and was given approval on Wednesday - started similar testing on teens and children in October.
The UK has ordered 40 million doses of the Pfizer vaccine, enough to vaccinate 20 million people - or about a third of the population - with two doses, given 21 days apart.
Health Secretary Matt Hancock said 800,000 doses of the jab will arrive from a Pfizer plant in Belgium next week, with millions more doses in the coming weeks.
The UK has ordered seven million doses of the Moderna jab.
Moderna has applied to America's FDA for emergency authorisation to begin vaccinating adults in the US, and is hopeful a roll out can begin by late December.
Speaking after final testing results were released, Stéphane Bancel, Chief Executive Officer of Moderna, said: "This positive primary analysis confirms the ability of our vaccine to prevent Covid-19 disease with 94.1% efficacy and importantly, the ability to prevent severe COVID-19 disease.
"We believe that our vaccine will provide a new and powerful tool that may change the course of this pandemic and help prevent severe disease, hospitalizations and death."
The results came from Moderna's Phase 3 study, which enrolled more than 30,000 participants in the US.
They found that there were 196 cases of Covid-19 across the trial group - 185 of which were in those taking the placebo, and 11 of which were given the vaccine.
The 196 Covid-19 cases included 33 older adults, and 42 participants identifying as being from diverse communities (including 29 Hispanic or Latin, 6 Black or African Americans, 4 Asian Americans and 3 multiracial participants).
Mr Bancel added: "We will file today for an Emergency Use Authorization from the FDA and continue forging ahead with the rolling reviews that have already been initiated with several regulatory agencies around the globe.”
