Covid-19: Pfizer/BioNTech vaccine judged safe for use in UK
Britain's medicines regulator, the MHRA, says the jab, which offers up to 95% protection against Covid-19 illness, is safe to be rolled out.
The first doses are already on their way to the UK, with 800,000 due in the coming days, Pfizer said.
Health Secretary Matt Hancock said the NHS will contact people about jabs.
Elderly people in care homes and care home staff have been placed top of the priority list, followed by over-80s and health and care staff.
But because hospitals already have the facilities to store the vaccine at -70C, as required, the very first vaccinations are likely to take place there - for care home staff, NHS staff and patients - so none of the vaccine is wasted.
A further 648 deaths within 28 days of a positive Covid-19 test were recorded in the UK on Wednesday, with another 16,170 cases reported.
Prime Minister Boris Johnson urged the public not to get "carried away with over optimism or falling into the naive belief that our struggle is over".
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