BioNTech's boss has warned that the mutated Covid variant spreading rapidly in the UK could make achieving herd immunity more difficult.
The German firm's co-founder Ugur Sahin warned officials may have to vaccinate almost three-quarters of the population, if the strain is proven to be more efficient at infecting people.
Currently experts say at least 60 per cent of a population need to have either caught the virus or be vaccinated against it to reach herd immunity, which is when a disease runs out of room and can no longer spread because too many people are immune to it, reports Daily Mail.
But more contagious bugs require more people to be protected against them.
For instance, around 95 per cent of people must be vaccinated against measles to stop it spreading.
Sahin also promised that, in the unlikely scenario the jab becomes ineffective, his team could re-engineer the vaccine to target the new variant within six weeks.
BioNTech, who worked alongside Pfizer to get their jab approved in Britain and the US, and Moderna both said today their coronavirus vaccines should work against the mutant strain spreading rapidly in the UK.
Moderna said it expects its jab to 'be protective' against the variant found in Britain. The US firm revealed that it is carrying out more trials in the coming weeks.
Test are being carried out to see if Pfizer/BioNTech's jab has the same 95 per cent effectiveness on the new strain as it does on the regular virus. Those results will be ready in a fortnight, Mr Sahin said.
But in attempt to calm fears about the variant, he added: 'Scientifically, it is highly likely that the immune response by this vaccine also can deal with the new virus variant.'
The comments come amid concerns the strain might make vaccines less effective because of the mutations that have occurred on the virus's spike protein, which it uses to latch onto human cells and cause illness.
Alterations to the spike are significant because most Covid vaccines, including Pfizer/BioNTech's approved jab, work by targeting this protein. It is feared these changes could also stop people from becoming immune if they have been infected with a different strain previously.
It comes as top scientists questioned the claim by Number 10's scientists the new strain was more infectious than regular Covid, saying there is 'no hard evidence' to prove it. Instead, the wave of cases in the South East may be the result of the disease spreading in a region where more of the population are susceptible it.
Professor David Livermore, a medical microbiologist at the University of East Anglia, said even if the strain is more infectious, it will likely be less lethal.
From an evolutionary standpoint, viruses can transmit more easily if they cause mild or asymptomatic illness because it means carriers continue to go about their daily lives, thereby spreading the contagion more extensively.
Raising the prospect of Britain having to vaccinate more people, Mr Sahin told the Wall Street Journal: 'If the virus becomes more efficient in infecting people, we might need even a higher vaccination rate to ensure that normal life can continue without interruption.'
Only 500,000 people have received the Pfizer/BioNTech vaccine in Britain since the biggest-ever inoculation drive began on December 8.
No10 has only bought 40million doses of the jab - enough to give to 20million people. It won't receive all the shots until later next year.
Britain could massively ramp up its programme with the Oxford University/AstraZeneca vaccine, which officials hope will be approved within days. Downing St has already ordered 100million doses of the jab, which trials have shown is at least 62 per cent effective.
Sahin added: 'We have scientific confidence that the vaccine might protect but we will only know it if the experiment is done... we will publish the data as soon as possible.'
But if needed, 'in principle the beauty of the messenger technology is that we can directly start to engineer a vaccine which completely mimics this new mutation - we could be able to provide a new vaccine technically within six weeks.'
Sahin said the variant detected in Britain has nine mutations, rather than just one as is usually common.
Nevertheless, he voiced confidence that the vaccine developed with Pfizer would be efficient because it 'contains more than 1,000 amino acids, and only nine of them have changed, so that means 99 percent of the protein is still the same'.
Moderna told CNN: 'Based on the data to date, we expect that the Moderna vaccine-induced immunity would be protective against the variants recently described in the UK; we will be performing additional tests in the coming weeks to confirm this expectation.'
While Pfizer, which teamed up with the German firm BioNTech to make their jab, said it was now 'generating data' on how well their vaccine works against the mutated type of coronavirus.
WHAT IS HERD IMMUNITY?
Herd immunity is a situation in which a population of people is protected from a disease because so many of them are unaffected by it - because they've already had it or have been vaccinated - that it cannot spread.
To cause an outbreak a disease-causing bacteria or virus must have a continuous supply of potential victims who are not immune to it.
Immunity is when your body knows exactly how to fight off a certain type of infection because it has encountered it before, either by having the illness in the past or through a vaccine.
When a virus or bacteria enters the body the immune system creates substances called antibodies, which are designed to destroy one specific type of bug.
When these have been created once, some of them remain in the body and the body also remembers how to make them again. Antibodies - alongside T cells - provide long-term protection, or immunity, against an illness.
If nobody is immune to an illness – as was the case at the beginning of the coronavirus outbreak – it can spread like wildfire.
However, if, for example, half of people have developed immunity – from a past infection or a vaccine – there are only half as many people the illness can spread to.
As more and more people become immune the bug finds it harder and harder to spread until its pool of victims becomes so small it can no longer spread at all.
The threshold for herd immunity is different for various illnesses, depending on how contagious they are – for measles, around 95 per cent of people must be vaccinated to it spreading.
For polio, which is less contagious, the threshold is about 80-85 per cent, according to the Oxford Vaccine Group.