A new vaccine that protects against Covid-19 is nearly 95% effective, early data from US company Moderna shows.
The results come hot on the heels of similar results from Pfizer, and add to growing confidence that vaccines can help end the pandemic.
Both companies used a highly innovative and experimental approach to designing their vaccines.
Moderna says it is a "great day" and they plan to apply for approval to use the vaccine in the next few weeks.
However, this is still early data and key questions remain unanswered.
How good is it?
The trial involved 30,000 people in the US with half being given two doses of the vaccine, four weeks apart. The rest had dummy injections.
The analysis was based on the first 95 to develop Covid-19 symptoms.
Only five of the Covid cases were in people given the vaccine, 90 were in those given the dummy treatment. The company says the vaccine is protecting 94.5% of people.
The data also shows there were 11 cases of severe Covid in the trial, but none happened in people who were immunised.
"The overall effectiveness has been remarkable... it's a great day," Tal Zaks, the chief medical officer at Moderna, told BBC News.
Dr Stephen Hoge, the company's president, said he "grinned ear to ear for a minute" when the results came in.
He told BBC News: "I don't think any of us really hoped that the vaccine would be 94% effective at preventing Covid-19 disease, that was really a stunning realisation."
When will I get it?
That depends on where you are in the world and how old you are.
Moderna says it will apply to regulators in the US in the coming weeks. It expects to have 20 million doses available in the country.
The company hopes to have up to one billion doses available for use around the world next year and is planning to seek approval in other countries too.
The UK government is still negotiating with Moderna as their vaccine is not one of the six already ordered. It says Moderna's will not be available before spring next year.
The UK has outlined plans that prioritise the oldest people for immunisation.
What don't we know?
We still do not know how long immunity will last as volunteers will have to be followed for much longer before that can be answered.
There are hints it offers some protection in older age groups, who are most at risk of dying from Covid, but there is not full data.
Mr Zaks told the BBC their data so far suggests the vaccine "does not appear to lose its potency" with age.
And it is not known whether the vaccine just stops people becoming severely ill, or if it stops them spreading the virus too.
All these questions will affect how a coronavirus vaccine is used.
Are there any side effects?
No significant safety concerns have been reported, but nothing, including paracetamol, is 100% safe.
Short lived fatigue, headache and pain were reported after the injection in some patients.
"These effects are what we would expect with a vaccine that is working and inducing a good immune response," said Prof Peter Openshaw, from Imperial College London.