Prime Minister Boris Johnson sought to strike a note of caution amid the excitement of the UK becoming the first country to approve the Pfizer/BioNTech vaccine against COVID-19, warning that it is not "game over" for the deadly virus just yet.
Johnson hailed the "searchlights of science" fighting back against the world's "invisible enemy" but urged people to not get carried away with over optimism over the course of the "long and cold months" ahead while the two-dose vaccine starts to be injected into the arms of those at the highest risk of death from the disease.
He urged people to follow the Covid Winter Plan of tiered lockdown which is now in force across England, with a majority of areas still under high alert measures of social distancing.
"It is a fantastic moment, but the worst thing now would be to think that this is the moment when we can relax our guard and think it's game over in the fight against COVID. It's not. This is not the end," Johnson said, during a briefing at 10 Downing Street on Wednesday evening.
"We have been waiting and hoping for the day when the searchlights of science would pick out our invisible enemy and give us the power to stop that enemy from making us ill - and now the scientists have done it," he said.
"It is all the more vital that as we celebrate this scientific achievement we are not carried away with over optimism, or fall into the naïve belief that the struggle is over. It's not, we've got to stick to our Winter Plan," he noted.
The UK PM confirmed that in line with the advice of the independent Joint Committee on Vaccination and Immunisation (JCVI), the first phase of the vaccine deployment will include care home residents, health and care staff, the elderly and those who are clinically extremely vulnerable.
"But there are immense logistical challenges: the vaccine must be stored at minus 70 degrees and each person needs two injections, three weeks apart. So it will inevitably take some months before all the most vulnerable are protected," he said.
"[But] we are no longer resting on the mere hope that we can return to normal next year in the spring, but rather on the sure and certain knowledge that we will succeed," he added.
His address came hours after the UK government confirmed that it has accepted the independent Medicines and Healthcare products Regulatory Agency (MHRA) assessment and authorised the use of Pfizer/BioNTech to immunise against COVID-19.
Now, authorisation has been granted, Pfizer will begin delivery of the vaccine to the UK. In making the recommendation to authorise supply, the MHRA will decide what additional quality assurance checks may be required before a vaccine can be made available.
The UK claims to be the first country to pre-order supplies of the vaccine from Pfizer/BioNTech, with 800,000 doses being made available next week and 40 million doses ordered overall - enough to vaccinate up to a third of the population, and the majority of doses anticipated in the first half of next year.