HERD immunity against coronavirus is mythical and unachievable, a leading panel of experts has said.

Scottish Government adviser Professor Devi Sridhar was among those speaking to the All Party Parliamentary Group (APPG) on Coronavirus this morning, when she said the country was unlikely to reach a threshold for herd immunity.

She also said that wealthy countries had seen “the worst” of Covid already, but the NHS may be overwhelmed this winter with other health issues instead of coronavirus.

The scientist, who is also a professor of global public health at Edinburgh University,  explained: “I think the world is becoming into two...We're having two pandemics, we're having the rich countries steam ahead and where, personally, I think the worst in terms of Covid is behind us.

“Vaccines, barring a very difficult variant, will hold up incredibly well and we are going to be looking at a health service overrun perhaps by other health issues that come back with a vengeance when people start to mix.”

On herd immunity, Professor Sridhar said: “I don't think we will reach one magical threshold of 95 per cent and the virus disappears.

“I think what we are likely to see, as we do with measles, is that it will find pockets of unvaccinated people who are susceptible and jump between them.

“Even with [the] Delta [variant] what you're seeing is people transmitting and being infectious and even getting Covid, while being fully vaccinated, so I don't think that we were likely to reach a threshold.”

Professor Sridhar added that there were still questions around vaccinating children, which should be the focus for wealthy nations which have already vaccinated the majority of their adult population.

She said: “For me, the biggest issue now is schools and what we do with under 16s, as we go forward in this world where adults are largely protected, but children are less susceptible.

“Are we ready for a large wave of infection in children? Or are there any fears associated with that?”

Professor Andrew Pollard, chairman of the UK’s vaccine watchdog said that herd immunity was “mythical” and vaccination strategies should not centre around achieving it.  

He added that vaccinating children would also not stop the spread of the disease.

He explained: “We know very clearly with coronavirus that this current variant, the Delta variant, will still infect people who have been vaccinated and that does mean that anyone who’s still unvaccinated, at some point, will meet the virus.”

He added: “I think we are in a situation here with this current variant where herd immunity is not a possibility because it still infects vaccinated individuals.”

He predicted that the next thing may be “a variant which is perhaps even better at transmitting in vaccinated populations”, adding: “So, that’s even more of a reason not to be making a vaccine programme around herd immunity.”

Professor Paul Hunter, from the University of East Anglia, said it was “absolutely inevitable” that variants would develop which can ‘escape’ the vaccine, and seasonal viruses will infect people “repeatedly…typically on average every four to five years”.

He said: “We are seeing this drift where mutations accumulate over time, so yes they will occur.

“A quarter of the UK population will, on average, get infected every year. What that means is that 45000 people a day, will be infected with coronaviruses.”

Professor Sridar was asked about how concerned we should be about these mutations, and she replied that vaccines were not an “on/off switch”.

She explained: “It’s about how much it brings it down and the real focus should be on severe infection, and people getting quite ill or prolonged illness.

“We need to be looking at layers of protection, to protect people from becoming severely ill and vaccines are one of them. If we can put in place testing regimes to stop people infecting others to keep transmission as low as possible, that’s another layer.

“Vaccines alone are not going to be enough in this world. They are a major pillar, but one of many tools.”

Professor Sridhar added that the pandemic was “far from over”, particularly for people who were immunocompromised, and it was important to explain to the public that the winter would be challenging.

She said it was possible to “do more living, and more mixing…but the pandemic is far from over in how it affects people’s lives.”

Paediatric critical care consultant Dr Ruchi Sinha told the APPG that there had been "a lot" of children who were obese in intensive care with Covid-19, and supported the idea of vaccinated clinically vulnerable children.

However, she did not think immunising all children aged 12-15 was the way forward. 

She said: "I do think we should be offering the vaccine to children who are vulnerable and more likely to suffer...

“Vaccine escape is inevitable and I think that it adds to the argument not to have a blanket rollout of the vaccine to children aged 12-15.”

She added: “With kids, they’re not going to stop transmission, they won’t stop variants, nothing is. It is about the risk to the child themselves.

“So, yes, we should offer it to vulnerable children. But I don’t think that currently, the way it stands, that vaccine rollout to all of them is the way forward.”