He said: "We're hoping very much that we will be able to avoid anything like that. But the reality is that the rates of infection have increased very much in the last few weeks."
Britain has ordered 100 million doses of the vaccines, four million of which are immediately available, allowing a major expansion in the NHS vaccine programme across the country.
Unlike the Pfizer jab, the Oxford vaccine can be stored in regular refrigerators, meaning it can be administered far more easily, from thousands of sites across the UK.
Authorisation by the MHRA will also give confidence to countries across the world. India has already manufactured more than 50 million of the AstraZeneca vaccines.
The NHS has drawn up plans for “large scale” vaccination sites, in football stadiums, racecourses and conference centres to start administering jabs from the first week of January.
The programme will also be expanded to high-street pharmacies, while the number of GP sites involved in the programme will continue to expand.
The rapid rollout of the programme has seen some teething problems this week, with some GPs complaining that deliveries have been cancelled with little notice, while others say they have been offered more jabs than they can keep up with.
However, health officials hope that the authorisation of the Oxford jab will prove a “game-changer”, allowing vaccines to be transported and administered far more easily.
Although the first batch of four million doses will be delivered from the Netherlands and Germany, the bulk of manufacturing will take place in this country, allowing for easy access.
AstraZeneca has said a further 15 million doses of active ingredients are ready, and can be filled into vials in a matter of days.
The full order of 100 million doses, in addition to 40 million doses of the Pfizer jabs being imported from Belgium, is enough to vaccinate the whole country. The speed of rollout means the majority of those aged 80 and over are likely to receive the Pfizer vaccine, which was authorised first.
Both types of vaccine require two doses, with a three-week gap between them for the Pfizer one, and a four-week gap for the AstraZeneca vaccine.
The AstraZeneca vaccine has taken longer for regulators to assess, because of differences in the efficacy rates found in different groups, ranging from 62 to 90 per cent. However, a study released this week suggests that leaving an adequate gap between doses is the most crucial way to boost efficacy.