Prime Minister Boris Johnson has said it will take “months” to inoculate everyone that needs a coronavirus vaccine despite a breakthrough with a British jab, as he warned that Christmas will be the season to be “jolly careful”.

The Prime Minister struck a cautious tone as he told the nation that “we’re not out of the woods yet” and that the UK faced a “hard” start to 2021, but that he expected “things will look and feel very different” after Easter.

He said that with a “favourable wind” the majority of people most in need of a vaccination might be able to get one by April, as the Oxford-AstraZeneca team said its jab had proved up to 90 per cent effective.

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It follows positive results from Pfizer and Moderna, but none of the jabs have yet been approved for use and getting people vaccinated will be a major undertaking.

Johnson, speaking via videolink at a Downing Street press conference as he continues his self-isolation, said: “We can hear the drumming hooves of the cavalry coming over the brow of the hill but they are not here yet.

“Even if all three vaccines are approved, even if the production timetables are met – and vaccines notoriously fall behind in their production timetables – it will be months before we can be sure we have inoculated everyone that needs a vaccine.”

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He warned that it is “not the moment to let the virus rip for the sake of Christmas parties”, saying: “Tis the season to be jolly, but it is also the season to be jolly careful, especially with elderly relatives.”

Johnson said that the months ahead “will be hard, they will be cold, they include January and February when the NHS is under its greatest pressure”.

That meant the need for new tiers from Wednesday December 2, replacing England’s lockdown, with more areas facing tougher restrictions than under the previous regional regime.

Under the new tier system:

• People will be able to leave their home for any purpose, and socialise with others in outdoor public spaces, subject to the rule of six. But only in Tier 1 will people be able to meet indoors with those not in their household or bubble.
• Collective worship and weddings will resume, though with a cap of 15 guests and receptions will be banned in Tier 3. Thirty people will be allowed to attend funerals, but only 15 will be able to attend a wake.
• Pubs and restaurants in Tier 3 will only be able to offer takeaway and delivery services, while indoor entertainment, hotels and other accommodation will close. In Tier 2, hospitality must close unless it is operating as a restaurant and in Tier 1 it will be table service only.
• In areas where hospitality venues are allowed to stay open, the 10pm curfew will be replaced with a last orders call at 10pm – but venues must close at 11pm.
• Retail and personal care – such as hairdressers and beauty salons – can reopen in all tiers, and indoor entertainment venues – such as cinemas, theatres, bowling alleys and casinos – will be allowed to stay open in Tiers 1 and 2, but not Tier 3.
• Gyms and swimming pools can reopen everywhere, though restrictions vary across the tiers for classes and organised adult sport. Spectator sport – and theatre – will be permitted in Tiers 1 and 2, though only drive-in events will be allowed in Tier 3.

Details of which areas will be in which tiers will be set out soon.

Meanwhile, a plan to allow families to be reunited for Christmas is being thrashed out with the leaders of Scotland, Wales and Northern Ireland, but Johnson was unable to confirm details.

England’s chief medical officer Professor Chris Whitty told the press conference that allowing families to mix at Christmas will have an “impact” on coronavirus cases and deaths, but said it could be minimised if people take restrictions seriously.

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He said: “If people do all those things very seriously we will have much less impact from Christmas whilst people are still being able to enjoy it, than if people choose to actually take a very much less public-spirited approach to it and go wild over that period.”

The latest figures showed a further 206 people had died within 28 days of testing positive for COVID-19 and there had been 15,450 more lab-confirmed cases.

As well as the progress on vaccines, Johnson pointed to the expansion of rapid mass testing as a way of returning to something approaching normality.