The vaccines minister says authorities are working to locate a person with a concerning variant of coronavirus.
Vaccines Minister Nadhim Zahawi has also confirmed that schools in England will reopen on 8 March.
Vaccines Minister Nadhim Zahawi says making Covid vaccine passports compulsory would be ''discriminatory''.
A study to see whether different vaccines can be used for the first and second dose of a coronavirus vaccine "will not impact our deployment programme", the vaccines minister has said.Copyright: BBC
The trial will be conducted in Birmingham and six other places.
Nadhim Zahawi, also Conservative MP for Stratford-on-Avon, told BBC Breakfast the government's rollout of vaccines would continue as planned.
"If you've had a Pfizer Biontech vaccine for your first dose, you'll have a Pfizer Biontech vaccine for your second.
"If you've had Oxford-AstraZeneca, you'll have Oxford-AstraZeneca for your second dose."
Eight hundred patients will be part of the study, which will report in the summer.
With one of the most pressing jobs in Government right now, who is the man responsible for England’s Covid 19 vaccination programme? With Mark Coles.
The EU has warned it will tighten exports of Covid vaccines produced in the bloc, amid a row with AstraZeneca over a cut in planned supplies.
Faith and community leaders have a big role to play in ensuring a high take-up of the coronavirus vaccine, vaccines minister, Nadhim Zahawi, has said.
He added the government was taking steps to tackle online disinformation around the vaccine, as well as making sure vaccine guidance was available in many different languages.
A recent poll, commissioned by the Royal Society of Public Health, suggested just over half of black, Asian and minority ethnic (BAME) people would be happy to have the coronavirus vaccine.Copyright: PA Media
The organisation also found certain ethnic and religious communities were being targeted with anti-vaccination messaging online.
These included querying the vaccine's longer-term effects and whether the ingredients were vegetarian or halal.
The UK's vaccine deployment minister welcomes the approval of a third vaccine.
By Sean Coughlan
The health minister appointed to oversee the rollout of the Covid vaccine in England has said the vaccination programme will not be compulsory.Copyright: PA Media
Nadhim Zahawi MP for Stratford-on-Avon, will oversee distribution of the vaccine until at least next summer.
He told Radio 4's World at One programme he hoped people would see the vaccine as a way to return to normality.
"I think it's right that it is voluntary - people have to be allowed to be able to decide for themselves when they want to be vaccinated or otherwise," he said.
"But I think the very strong message that you will see - this is the way we return the whole country so it's good for your family, it's good for your community, it's good for your country to be vaccinated.
"Ultimately people will have to make a decision."