The public has been urged to be vigilant as fraudsters demand elderly and vulnerable people provide bank details or cash payments for access to fake Covid-19 vaccines.
The National Economic Crime Centre (NECC) said in a statement legitimate coronavirus vaccines were free and would be distributed by the NHS in England, Northern Ireland, Wales and Scotland.
Security minister James Brokenshire said: "It's a sad reality that scammers and fraudsters are using the pandemic to fleece innocent people out of their hard-earned cash.
"If you receive an email, text message or phone call claiming to be from the NHS and you are asked to provide financial details, or pay for the vaccine, this is a scam."
The warning comes after a fraudster claiming to work for the NHS jabbed a 92-year-old woman with a fake Covid-19 vaccine.
Detectives hunting the suspected conman, who charged the victim £160, say he "may endanger people's lives".
The victim allowed him into her home in Surbiton, south-west London, on the afternoon of Wednesday December 30 after he said he was from the NHS and there to administer the Covid-19 vaccine.
She said she was jabbed in the arm with a "dart like implement" before being charged £160 which the fraudster said would be refunded by the NHS.
The City of London Police said it is not known what substance, if any, was administered, but the woman showed no ill effects after a check at her local hospital.
The NECC said the NHS will never ask people for a bank account or card details, will not request a PIN or banking password and will not arrive announced at someone's home to administer the vaccine.
The UK has recorded its highest number of Covid-19 deaths reported on a single day since the pandemic began, while figures for cases and hospital admissions have also hit record levels.
In a more positive development, a third Covid-19 vaccine, from US biotech firm Moderna, was given the green light by the Medicines and Healthcare products Regulatory Agency (MHRA) on Friday – joining the vaccines from Pfizer/BioNTech and Oxford/AstraZeneca.