A COVID-19 vaccine being developed by biotech company Moderna is almost 95 per cent effective at preventing the disease, according to early data from clinical trials.

Moderna said on Monday that an analysis of its clinical trial of the vaccine showed effectiveness rates of 94.5 per cent. 

"This positive interim analysis from our Phase 3 study has given us the first clinical validation that our vaccine can prevent COVID-19 disease, including severe disease," said Stephane Bancel, Moderna's CEO.

The company said it will be applying for emergency approval of the vaccine by the US' Food and Drug Administration in the coming weeks and expects to have 20 million vaccine doses available for the US by the end of the year.

Moderna, which has received $2 billion from the US government under "Operation Warp Speed," added it is on track to manufacture between 500 million to a billion doses globally in 2021.

Global infections from COVID-19 have soared past 54 million with more than 1.3 million deaths since the virus emerged in China late last year.

The Moderna vaccine, which was co-developed by the US National Institutes of Health, is given in two doses 28 days apart.  

It is the second COVID-19 vaccine in development to report highly promising test results. Last week, Pfizer reported that a vaccine it is working on with BioNTech appears to be 90 per cent effective at preventing the disease.

Ten other companies are currently conducting phase 3 trials of experimental COVID-19 vaccines, with dozens more in earlier stages of testing.  

How the vaccine works

Both frontrunners are based on new technology that uses synthetic versions of molecules called "messenger RNA" to hack into human cells, and effectively turn them into vaccine-making factories.

The promising results of both vaccines are seen as a validation for mRNA technology, which has never before been brought to regulatory approval.

It works by providing human cells with the genetic instructions to make a surface protein of the coronavirus, which trains the immune system to recognise the real virus.

Making a traditional vaccine is a longer process that normally involves developing a weakened form of a pathogen. 

While both vaccines appear to be highly promising, the data is still considered preliminary and many key questions - such as how long the vaccines confer immunity for, or whether they are equally effective among all age groups - remain unanswered at this stage. 

Another open question is whether they stop people who are exposed to the virus from transmitting it on to the other people, even though they may be themselves protected from the disease.

Clinical trials for both the Pfizer and Moderna vaccines are still under way and their efficiency numbers are subject to change.

How Moderna tested its vaccine

Moderna’s trial involved 30,000 test subjects. Half of those were given two doses of the experimental vaccine, two weeks apart. The other half were given a placebo shot of saltwater. 

The company analysed the first 95 people among those test subjects to report COVID-19 infection. 90 came from the cohort given a placebo, while only five of those cases were among those given the vaccine. 

There were 11 people who fell severely ill, all of whom were in the placebo group.

How the vaccine candidate works. Video: Moderna

Storing the vaccine 

While the Pfizer vaccine must be stored at temperatures of around minus 75 Celcius and can survive in a standard fridge for roughly five days, Moderna says its vaccine candidate can be stored at minus 20 Celcius for up to six months, will survive in a standard fridge for up to a month and can be kept at room temperature for 12 hours.

Moderna has said its vaccine will not require any dilution or special handling. 

On the downside, Moderna's vaccine has about three times more genetic material per dose than its Pfizer counterpart, Zoltan Kis, a research associate at Imperial College's Future Vaccine Manufacturing Hub, said. 

This would raise production costs and make it harder to scale-up.

So far, neither vaccine trial has reported serious side-effects, though some participants have reported fatigue, fever and muscle pains lasting one or two days. 

Biden, Trump welcome news

"Today's news of a second vaccine is further reason to feel hopeful," tweeted President-elect Joe Biden, but he cautioned that its widespread distribution was months away.

"Until then, Americans need to continue to practice social-distancing and mask-wearing to get the virus under control," he said.

President Donald Trump also weighed in on Twitter, to take credit. "Please remember that these great discoveries, which will end the China Plague, all took place on my watch!" 

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