The World Health Organisation has warned there will not be enough vaccine stock to prevent more surges in coronavirus cases over the next three to six months.
Dr Mike Ryan, executive director of WHO’s health emergencies programme, made the stark warning during a social media event as he called on people to maintain social distancing to restrict the spread of Covid-19.
He said: “We are not going to have sufficient vaccinations in place to prevent a surge in cases for three to six months.”
His comments on Wednesday came after the UK became the first country in the world to approve a Covid-19 jab from Pfizer and BioNTech.
The vaccine, which studies have shown is 95 per cent effective and works in all age groups, will be rolled out in the UK from next week.
The European Union has criticised Britain's rapid approval of Pfizer's vaccine, saying its own procedure is more thorough.
In an unusually blunt statement, the European Medicines Agency (EMA), which is in charge of approving Covid-19 vaccines for the EU, said its longer approval procedure was more appropriate as it was based on more evidence and required more checks than the emergency procedure chosen by the UK.
German MEP Peter Liese, a member of the European Parliament's public health committee, said individual EU member states could have authorised the vaccine but had chosen to wait for the EMA to examine more information rather than follow the "hasty" UK example.
The EMA said it would decide by 29 December whether to provisionally authorise the vaccine from US drugmaker Pfizer Inc and its German partner BioNTech. The vaccine is set to be reviewed by a panel of experts a week earlier before the FDA decides whether to authorise its use in the US.
Moderna, one of the front-runners in the race to develop a coronavirus vaccine, has applied for emergency authorisations both in the US and the EU after full results from a late-stage study showed its vaccine was 94.1 per cent effective with no serious safety concerns.
On the same day the Pfizer-BioNTech jab was approved in the UK, Boris Johnson said the NHS would embark on the the “biggest programme of mass vaccination” in the country’s history from next week.
Simon Stevens, the NHS England chief executive, said the plan is for over-80s and people in care homes to get vaccinated first, together with "some of the frontline health and social care staff who are looking after them".
He said the bulk of vaccinations will take place in "January through to March or April for the at-risk population".
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The UK has ordered 40 million doses of the Pfizer vaccine, which is enough to vaccinate 20 million people with two doses, given 21 days apart.
Matt Hancock, the UK health secretary, said 800,000 doses of the jab will arrive next week, with millions more arriving in the coming weeks.
BioNTech's Mr Marett said the UK was likely to receive at least five million doses of vaccine by the end of the year. The UK had initially expected 10 million by the end of December, but Mr Marett said the amount being shipped out was being scaled back for all orders.
Additional reporting by agencies