A fake article claimed Elisa Granato had died following complications after taking the vaccine.
One of the first people to be injected as part of UK human trials for a coronavirus vaccine has said she is "doing fine", after a fake article about her death was circulated on social media.
The article claims the Oxford microbiologist, who took part in the trial on Thursday, had died.
The Government later said the article is "completely untrue", and warned people about sharing unsubstantiated claims online.
Dr Elisa Granato was one of two people to take part in the trial, and said she was "excited" to support the efforts by volunteering.
Following the article about her "death", she tweeted about the news before making her Twitter account private.
She wrote: "Nothing like waking up to a fake article on your death ... I'm doing fine everyone."
On Sunday afternoon, the Department of Health and Social Care tweeted: "News circulating on social media that the first volunteer in a UK coronavirus vaccine trial has died is completely untrue.
"Before sharing unsubstantiated claims online, use the Share checklist to help stop the spread of harmful content."
Earlier this month, the Government relaunched its Don't Feed The Beast public information campaign to encourage people to question what they read online.
The Share checklist includes basic advice, such as checking the source of a story and analysing the facts before sharing.
A Rapid Response Unit, operating from within the Cabinet Office and No 10, is tackling a range of harmful narratives online and co-ordinating with departments across Whitehall to deploy the appropriate response, which can include a direct rebuttal on social media, working with platforms to remove harmful content and ensuring public health campaigns are promoted through reliable sources.
The unit is one of the teams feeding into the wider Counter Disinformation Cell led by the Department for Digital, Culture, Media and Sport, made up of experts from across government and in the tech sector.
The cell is engaging with social media platforms, and with disinformation specialists from civil society and academia, to establish a comprehensive overview of the extent, scope and impact of disinformation related to coronavirus.
A Covid-19 vaccine is considered the ultimate exit strategy by many experts, and scientists across the world are racing to develop one that can be produced at scale.
The Oxford Vaccine Group hopes to have at least a million doses of its candidate ready in September.