The NHS has warned people to be vigilant about fake invitations to have the coronavirus vaccination, sent by scammers.
The scam email includes a link to "register" for the vaccine, but no registration for the real vaccination is required.
The fake site also asks for bank details either to verify identification or to make a payment.
The NHS says it would never ask for bank details, and the vaccine is free.
Cyber-security consultant Daniel Card told BBC News that traffic data indicates thousands of people had clicked the link to the fake site - although it is unclear how many then filled in the form.
Allow Twitter content?
He urged people to remain vigilant: "These things spring up, we take them down and then they spring up again."
Both the National Cyber Security Centre and Action Fraud have asked anyone who receives a scam email or text to report it.
"Vaccines are our way out of this pandemic," said health secretary Matt Hancock.
"It is vital that we do not let a small number of unscrupulous fraudsters undermine the huge team effort under way across the country to protect millions of people from this terrible disease."
At the start of January, Derbyshire police issued a warning about a text message scam which offered Covid vaccinations.
"If you receive a text or email that asks you to click on a link or for you to provide information, such as your name, credit card or bank details, it's a scam," the force said.
Last year, tech firms warned that coronavirus was a popular hook for scammers. In April 2020 Google said it was blocking 18 million scam emails a day on the subject.