A second US-developed vaccine has had a high success rate in protecting people from the coronavirus, raising hopes of an imminent cure to the global pandemic.

Moderna Inc’s experimental vaccine was 94.5 per cent effective based on interim data from a late-stage trial, the company said, as it prepares to seek approvals in the US within weeks.

The medical breakthrough comes hot on the heels of Pfizer’s recent announcement that its vaccine was more than 90 per cent effective.

Pending more safety data and regulatory review, the US could have two vaccines authorised for emergency use in December with as many as 60 million doses available in 2020.

Next year, the US government could have access to more than 1 billion doses just from the two vaccine makers, more than needed for the country’s 330 million residents.

“This news from Moderna is tremendously exciting and considerably boosts optimism that we will have a choice of good vaccines in the next few months,” said Peter Openshaw, professor of experimental medicine at Imperial College London.

Moderna president Stephen Hoge said: “We are going to have a vaccine that can stop COVID-19.”

• Related: Coronavirus vaccines: A form guide

Both vaccines are powerful tools to fight a pandemic that has infected 54 million people worldwide and killed 1.3 million and has been worsening.

COVID-19 cases have hit new records in the US – increasing from 10 million infections to 11 million in a week – and pushed some European countries back into lockdown.

WHO chief scientist Soumya Swaminathan said Moderna’s news was “quite encouraging” but more data was needed.

She said trial participants needed to be monitored for two more months for possible side effects.

“There are many questions still remaining” about the Moderna product and about Pfizer’s rival vaccine candidate that has also shown to be very effective in trials, Ms Swaminathan said.

Moderna’s interim analysis was based on a trial involving 30,000 US adults including high-risk or elderly people.

Half were given two doses administered 28 days apart and the other half were given a placebo.

The analysis looked at the first 95 people to become infected and found only five infections occurred in those who received the vaccine.

Of the 95 cases, 11 were severe and all 11 occurred among volunteers who were not given the vaccine.

The data also showed the Moderna vaccine prevented cases of severe COVID-19, a question that still remains with the Pfizer vaccine.

Moderna expects to have enough safety data required for US authorisation in the next week or so and the company expects to file for emergency use authorisation (EUA) in the coming weeks.

A key advantage of Moderna’s vaccine is that it does not need ultra-cold storage like Pfizer’s, making it easier to distribute.

Moderna expects it to be stable at normal fridge temperatures of 2-8 degrees for 30 days and it can be stored for up to six months at -20 degrees.

Pfizer’s vaccine must be shipped and stored at -70 degrees, the sort of temperature typical of an Antarctic winter.

It can be stored for up to five days at standard refrigerator temperatures or for up to 15 days in a thermal shipping box.

Moderna, part of the US government’s Operation Warp Speed program, expects to produce about 20 million doses for the US this year, millions of which the company has already made and is ready to ship if it gets FDA authorisation.

“Assuming we get an emergency use authorisation, we’ll be ready to ship through Warp Speed almost in hours,” Mr Hoge said.

“So it could start being distributed instantly.”

The 95 cases of COVID-19 included several key groups who are at increased risk for severe disease, including 15 cases in adults aged 65 and older and 20 in participants from racially diverse groups.

“We will need much more data and a full report or publication to see if the benefit is consistent across all groups, notably the elderly, but this is definitely encouraging progress, said Stephen Evans, professor of pharmacoepidemiology, London School of Hygiene and Tropical Medicine.

Most side effects were mild to moderate.

A significant proportion of volunteers, however, experienced more severe aches and pains after taking the second dose, including about 10 per cent who had fatigue severe enough to interfere with daily activities while another 9 per cent had severe body aches.

Most of these complaints were generally short-lived, Moderna said.

Its data provide further validation of the promising but previously unproven mRNA platform, which turns the human body into a vaccine factory by coaxing cells to make certain virus proteins that the immune system sees as a threat and mounts a response against.

-with AAP