The jab, made by US firm Novavax, is based on protein rather than genetic material from the virus.

The UK Vaccine Taskforce placed an order for 60 million doses in 2020, and the government had originally expected they would be available in the second half of 2021.

But the vaccine has been delayed by manufacturing problems and the regulatory process - and jabs from Pfizer, Moderna and Astra-Zeneca have since become the backbone of the UK rollout.

The delay caused problems for more than 15,000 people in the UK who volunteered for clinical trials of the jab.

They were unable to travel because many countries required proof of immunisation with a vaccine that had been approved by medical authorities.

The government announced last October that the volunteers would be given 'top-up' doses with the Pfizer jab so they could qualify for a vaccine pass abroad.

The Novavax vaccine has been approved by the Medicines and Healthcare products Regulatory Agency (MHRA) for use in adults over the age of 18.

Stanley Erck, President and Chief Executive Officer of the company, said: "We are proud that Nuvaxovid will be the first protein-based vaccine option authorised by the MHRA as the United Kingdom tackles this next phase of the pandemic.

"We thank the agency for its thorough review process and are tremendously grateful to the clinical trial participants and trial sites in the UK, as well as the Vaccine Taskforce, for their ongoing support and vital contributions to this program."