Moderna’s coronavirus vaccine has become the second to be approved for emergency use in the US.
The country’s Food and Drug Administration announced the authorisation a day after the agency’s panel of outside experts backed the vaccine.
The FDA based its decision on results from a late-stage study of 30,000 volunteers which found that the vaccine was nearly 95% effective at preventing illness from COVID-19.
The study also said there were no serious safety concerns resulting from the vaccine’s use, although possible side effects include sore arms, fever, fatigue and muscle aches.
National Institutes of Health Director Dr Francis Collins said: “We’re not done with this but hope is on the way, and the hope comes from this scientific brain trust that has pulled out all the stops.”
The US is the first country to authorise use of the Moderna vaccine – European regulators could approve it as early as 6 January and the UK could also approve it soon.
Moderna says it is prepared to distribute 5.9 million shots in the US as early as this weekend, news that will bring some comfort in a country that has already lost more than 313,000 people to the virus.
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An average of 216,000 people in the US test positive for the disease each day and hospitals are struggling to keep up with the number of patients suffering serious complications.
The US has already approved use of a vaccine by Pfizer and BioNTech but the Moderna vaccine is easier to store and distribute, capable of remaining stable at -20C – equal to most household or medical freezers – for up to six months.
Dr Collins said both vaccines had undergone unprecedented rigorous analysis but officials still worry that some members of the public might still need persuading to accept the vaccine.
Like the Pfizer vaccine, Moderna’s uses a piece of genetic code that trains the immune system to recognise the virus and attack it. Both require two jabs several weeks apart.
The Moderna vaccine was found to be especially effective in older adults, who are most vulnerable to complications from the disease.
However, like the Pfizer version, it is not clear whether the Moderna jab prevents asymptomatic spread.