The variant of coronavirus first identified in India is likely to become a “variant of concern” which could potentially lead to the country being put on the UK’s travel “red list”, an immunology expert has said.

Danny Altmann, professor of immunology at Imperial College London, said variants of the virus which causes Covid-19 “do pose a threat” and vulnerable people could be “caught out”.

Dozens of cases of the variant have been identified in the UK.

The variant, also known as B.1.617, is currently designated as a “variant under investigation” (VUI) rather than a “variant of concern” (VOC), such as those first identified in Kent, Manaus (Brazil) or South Africa.

Prof Altmann said some people in the population are still vulnerable and can “still be caught out” by variants.

He told ITV’s Good Morning Britain: “I am concerned about all the variants. Don’t get me wrong, I think our road map is going well and at the moment, in this country, we are doing rather well, enjoying unlocking.

“But out there, there is the Indian variant, the South African, Brazilian etc, and they do pose a threat.”

He added: “At the moment, we are still vulnerable, and some people in our population are still vulnerable – what I mean by that is the Indian variant, for example, certainly has a mutation like the ones that evade the best neutralising antibodies.

“What that means is, if you have a population where at least half of us have had zero or one dose of vaccine, some won’t have made a very good response to the vaccine, because perhaps they are very old or obese or unwell, we still have a very large vulnerable population who can still be caught out by variants like this.

“At the moment, this particular variant is called a variant under investigation, not a variant of concern because it hasn’t been escalated to that level yet.

“My assumption from everything I’ve seen is that it will become a variant of concern.

“When it becomes a variant of concern, I’d be quite surprised if India wasn’t on the red list.”

Dr Jeffrey Barrett, director of the Covid-19 Genomics Initiative at the Wellcome Sanger Institute, said that the variant of the virus first identified in India should be “watched carefully” but it is “probably not at the top tier of mutations that generate the most concern”.

He told BBC Radio 4’s Today programme that the first cases of the variant were identified late last year.

“This variant has a couple of mutations that are among those that we think are important that should be watched carefully, but they’re actually probably not at the very kind of top tier of mutations, for example in the B117 – or Kent variant – or the South African variant, that generate the most concern.

“And in terms of spread, clearly this variant has increased in frequency in India around the same time as their very large and tragic recent wave,

“But I just don’t think we know yet whether there’s a cause-and-effect relationship – is this variant driving that spread? Or is it happening at the same time perhaps due to a coincidence?”

He added: “And one thing to note is that there were some sequences of this variant B.1.617 seen late last year. And so in some sense, if it really is driving this wave, the fuse has been burning for quite a long time, which would make it look probably less transmissible than B117.”

When asked whether India should be placed on the so-called “red list” for travel, Andrew Hayward, professor of infectious disease epidemiology at University College London, said his preference was to “err on the side of caution and act sooner rather than later”, but that the decision was a political one.

Prof Hayward, who is on the Scientific Advisory Group for Emergencies (Sage), and also a member of the New and Emerging Respiratory Virus Threats Advisory Group (Nervtag), told the Today programme: “The evidence of increased transmissibility and escape from immunity is circumstantial.

“That said, it’s going to take a number of weeks at least before that evidence gets firmed up and we find out more.

“Certainly some countries and areas have taken the view that that’s enough for them to be quite concerned – so for example, Hong Kong has put on a two-week travel ban, which will allow them to find out a little bit more.”

Asked if he would be in favour of India being put on the travel red list, he said: “It’s a balance of harms and benefits and the challenge with that is that the level of harm is quite high because we’re highly connected with India – there’s a lot of economic interaction as well as family and social interaction.

“And on the other hand, what we have is an unknown level of risk – my own preference in all of this is to err on the side of caution and to act sooner rather than later. But ultimately, that’s going to be a political decision.”

According to the latest update from Public Health England (PHE), 73 cases of the B.1.617 variant, which was first discovered in India, have been found in England, as well as four cases in Scotland.

There are four so-called “variants of concern” and seven “variants under investigation” which have been identified in the UK.

Prime Minister Boris Johnson is due to travel to India in the last week of April in a trip that has already been cut short as infections in the country continue to climb.

But the Government has faced calls to move India to the travel “red list”, which would mean only UK nationals could return from the country and those doing so must pay to quarantine in a Government-approved hotel for 10 days.