The findings, led by the National Institutes of Health, have not been peer-reviewed or published, but Professor Robin Shattock, Professor of Mucosal Infection and Immunity, Imperial College London, called the early results "encouraging".
He added: "This is a promising start, but efficacy data will be key followed by an ability to scale in a manner that provides global access should this vaccine be successful."
US president, Donald Trump, has said the of any vaccines developed before they are fully approved so that they can be quickly distributed once rubber-stamped.
But the president has accused the US Food and Drug Administration of preventing pharmaceutical companies from finding people to test coronavirus vaccines on. Mr Trump suggested .
It has also been reported that to develop a coronavirus treatment, and plan to have a vaccine ready for testing by the end of 2020.
Germany announced it on the brink of clinical trials for a coronavirus vaccine.
Its purchase of a 23 per cent stake in CureVac comes after reported attempts by the Trump administration to court the firm and secure supply of any future vaccine sparked political backlash in Berlin. CureVac rejected claims in March that it had received acquisition offers for the company or its technology.
Positive early results for Chinese drug company
On June 17, a of a vaccine, claiming it induced an immune response in 100 per cent of those who were given it.
The vaccine is being developed by the firm China National Biotec Group (CNBG) and is one of the in the race to develop an effective inoculation against the disease.
, also announced positive results for its coronavirus vaccine, saying it was hoping to move to large-scale phase three trials in Brazil soon.
Africa’s first participation in a Covid-19 vaccine trial started on June 24 as volunteers received injections developed at the University of Oxford, while officials said the continent of 1.3 billion people cannot be left behind.
The large-scale trial .
Other treatments being trialled
Alongside vaccine development, doctors are for viruses such as Ebola, malaria and HIV. Early results seem promising but, until full clinical trials have been concluded, doctors cannot be certain that the drugs are effective.
The , originally a malaria drug, was hailed by Matt Hancock, the Health Secretary, in April as a "major milestone" in the battle against Covid-19.
However, the results of an international study by WHO indicate that it increases the chances of death for hospitalised patients by nine to 21 per cent.
The organisation , citing safety concerns. But on May 26, the leaders of the Oxford-led Recovery trial, which operates in NHS hospitals, said they would continue on the basis their data did not show an increased risk.
AstraZeneca has started a Phase 1 clinical trial of its drug AZD7442, a combination of two monoclonal antibodies, for the prevention and treatment of Covid-19. The trial, funded by the US Government, will include up to 48 healthy participants in the UK aged 18 to 55.
A so-called monoclonal antibody combination works by mimicking the body's natural antibodies.
The world's first coronavirus treatment that significantly reduces the risk of death is being given to NHS patients following .
In a breakthrough described by Boris Johnson, the Prime Minister, as a "remarkable achievement", the common steroid dexamethasone was shown to radically improve the chances of survival for the most ill patients.
On June 16, Mr Johnson hailed the result as the "biggest breakthrough yet" in the treatment of coronavirus, both in Britain and globally.
The Government has been stockpiling dexamethasone since March in case the trials were successful. There are already supplies for 200,000 patients, and enough to cope with any second wave of the virus.
The drug – commonly used to treat arthritis, severe allergies and – costs just £5 for a full course of treatment and is expected to have a major impact on the pandemic.
Scientists at Oxford University, who have been on a number of drugs since March, announced that a 10-day course of dexamethasone lowers the risk of death for people on ventilators by one third.
The researchers said the drug should become the standard of care in the most sick patients.
UK vaccine taskforce
On April 17, the government - set up under the Department for Business, Education and Industrial Strategy (BEIS) - designed to "rapidly develop a coronavirus vaccine", as well as scale up manufacturing so it can be quickly produced and delivered in mass quantities.
It is led by Sir Patrick Vallance and Professor Jonathan van Tam, Deputy Chief Medical Officer, and members will include pharmaceutical companies, such as AstraZeneca, as well as the Wellcome Trust.
The government has initially earmarked £14 million to plough into 21 coronavirus research projects - such as the work by the scientists at the University of Oxford and Imperial College London. On April 21, an announcement of a further £44.5 million for the Oxford and Imperial trials increased this funding further still.
A few weeks later the Business Secretary, Alok Sharma announced a further £84 million in new funding "to help accelerate their work".
He said: "This new money will help mass-produce the Oxford vaccine so that if current trials are successful we have dosages to start vaccinating the UK population straight away."
To help the UK mass produce a vaccine, Mr Sharma has announced the UK's first vaccines manufacturing innovation centre is expected to open in summer 2021, a year ahead of schedule.
He said: "To further support our domestic manufacturing capabilities last month, I announced the Government would accelerate building the UK's first vaccines manufacturing innovation centre, which is based at Harwell in Oxfordshire.
"And today I can announce we will invest up to a further £93 million in the centre ensuring that it opens in summer 2021, a full 12 months ahead of schedule. "The centre, which is already under construction, will have capacity to produce enough vaccine doses to serve the entire UK population in as little as six months."