Boris Johnson is to lead a Downing Street press conference on coronavirus at 5pm on Tuesday.
The prime minister will appear alongside chief medical officer Chris Whitty and Simon Stevens, chief executive of the NHS.
Johnson is likely to face questions on the unfolding row between the EU and Oxford vaccine manufacturer AstraZeneca, which could lead to the European Commission restricting much-needed Pfizer jabs manufactured in the bloc.
It comes after the company told the bloc on Friday that its first vaccine deliveries would be up to 60% lower than initially promised.
The PM is thought to be angry after reports in the German media, thought to have originated from an official in Berlin, suggested the Oxford/AstraZeneca jab has an efficacy of less than 10 per cent for the elderly.
Both Germany and AstraZeneca both strongly denied the reports were correct, with the pharmaceutical giant dismissing the claim as “completely incorrect”.
Downing Street said chief scientific officer Patrick Vallance told a meeting of Johnson’s Cabinet on Tuesday that the Oxford/AstraZeneca vaccine had shown to be effective in both younger and older people.
Boris Johnson’s official spokesperson told reporters: “Cabinet discussed the latest on Covid-19, with the Prime Minister once again paying tribute to the British public for the sacrifices they continue to make in our fight against the virus.
“The prime minister highlighted that while we are now seeing signs of new case numbers reducing, we can anticipate that intense pressure in hospitals and high death rates will persist in coming weeks, underlining the importance of continuing to follow the rules.
“He also pointed to the fact that more than 6.5 million people in the UK have now received their first vaccine dose, including three-quarters of all over-80s and eligible care home residents.
“The chief scientific adviser set out that the Oxford/AstraZeneca vaccine remains both safe and effective and that the trials showed similar immune responses in both younger and older adults.”
The Cabinet also discussed new measures which could see people arriving in the UK from abroad quarantined in hotels. It is part of a bid to stop any more new variants of the disease reaching Britain.
Johnson is also under increasing pressure to outline when schools will return, amid fears children will not be back in classrooms before Easter break in April.
It is expected that the daily death toll from Covid-19 will exceed 100,000 in the coming days.