The UK has become the first country in the world to approve the Pfizer/BioNTech coronavirus vaccine for widespread use.
British regulator, the MHRA, says the jab, which offers up to 95% protection against Covid-19 illness, is safe for rollout next week.
Immunisations could start within days for people who need it the most.
The UK has already ordered 40m doses – enough to vaccinate 20m people, with two shots each.
Around 10m doses should be available soon, with the first 800,000 arriving in the UK in the coming days.
It is the fastest ever vaccine to go from concept to reality, taking only 10 months to follow the same developmental steps that normally span a decade.
Health Secretary Matt Hancock tweeted saying: “Help is on its way.”
NHS Chief Executive, Sir Simon Stevens, said the health service was preparing for “the largest-scale vaccination campaign in our country’s history”.
Around 50 hospitals are on standby and vaccination centres in venues such as conference centres are being set up now.
Although vaccination can start, people still need to remain vigilant and follow coronavirus rules to stop the spread, say experts.
That means sticking with the social distancing and face masks, and testing people who may have the virus and asking them to isolate.
What is the vaccine?
It is a new type called an mRNA vaccine that uses a tiny fragment of genetic code from the pandemic virus to teach the body how to fight Covid-19 and build immunity.
An mRNA vaccine has never been approved for use in humans before, although people have received them in clinical trials.