Vaccination alone will not be enough to bring coronavirus in the community down to “very low levels”, and social restrictions may have to continue until around 50 per cent of the population has been vaccinated, an expert has said.


Many people have been hoping for a return to normal once the elderly and those most at risk from COVID-19 have received the jab.

But scientists say this might not be enough to see an end to measures such as social distancing and wearing face masks.

They suggest restrictions may be needed until at least half of the UK’s population has had the coronavirus vaccine.

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Stephen Evans, professor of pharmacoepidemiology at the London School of Hygiene and Tropical Medicine, said vaccination alone will not be enough to bring the virus circulating in the community to “very low levels”.

“We actually need to have the absolute amount of virus circulating to be very low," said Evans at a press briefing arranged by the Science Media Centre.

“And we won’t do that by vaccination alone until we’re getting 50 per cent of the population vaccinated or more, and that’s going to be quite a bit of a long way off yet.

“So I fear that the sort of restrictions we have, the non-medical interventions, are going to need to be carried on.”

“I think if people take these seriously, then it’s possible for various economic activities to go ahead, but you have to make sure that you are keeping to the non-medical interventions, being aware and behaving as if every person you contact has got the virus. And that you have it as well," added Evans.

“And when you behave in a way that realises that, and that the consequences for either you or the person around you getting the virus can be very serious, then it changes people’s behaviour.

“And we’re going to have to go on doing that for quite a long time.”

Health Secretary Matt Hancock said that as of 8am on Saturday 19 December 2020, 350,000 people had been vaccinated.

Do I need the coronavirus vaccine if I’ve already had COVID? © Getty Images
Vaccination alone won't reduce the circulation of the virus until over half of the population have been immunised, say experts © Getty Images

Adam Finn, professor of paediatrics at the University of Bristol, said that even if the elderly are vaccinated, social restrictions may have to continue for some time.

“I think the modelling is very clear that even if you had high coverage and high levels of protection in the high-risk groups, you would still see epidemics, and large numbers of hospitalisations and deaths if you relax the measures before you have a broader control of viral circulation in the population at large," said Finn.

“So I think the idea that you can immunise a large proportion of the elderly and then kind of go back to normal is misguided.

“I think that none of the models suggest that that’s going to be possible.”

Peter Openshaw, professor of experimental medicine at Imperial College London, said he is concerned about the hard to reach in the community – people who are very doubtful about vaccines or those not very well informed. He said this is something that needs to be focused on.

He added that the efficacy of the Oxford-AstraZeneca vaccine, which is yet to receive regulatory approval, against transmission may be “considerable” even if it is not as effective as the other options.

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There have been some concerns the Oxford vaccine may not be as good as preventing symptomatic disease as the others, but the experts suggested it would be adequate for very strong population-wide effects if widely deployed.

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The experts said it is not yet possible to say how much of the population needs to be vaccinated to achieve herd immunity.

They explained that while there is insufficient evidence on how effective the vaccines are at reducing transmission, the Pfizer vaccine developed with BioNTech and the Moderna jabs have demonstrated such high efficacy, it would be surprising if there was no impact on transmission.

Openshaw explained that as well as the elderly, there has to be concern about the effects of long COVID in relatively young people.

He said he found the idea of his colleagues or his relatives becoming affected by long COVID “terrifying”.


“We shouldn’t stop vaccinating once we have just vaccinated the high risk," said Openshaw. “I think we have to get the population vaccinated and I think the prospects of vaccines preventing long COVID are quite good.”

How do scientists develop vaccines for new viruses?

Vaccines work by fooling our bodies into thinking that we’ve been infected by a virus. Our body mounts an immune response, and builds a memory of that virus which will enable us to fight it in the future.

Viruses and the immune system interact in complex ways, so there are many different approaches to developing an effective vaccine. The two most common types are inactivated vaccines (which use harmless viruses that have been ‘killed’, but which still activate the immune system), and attenuated vaccines (which use live viruses that have been modified so that they trigger an immune response without causing us harm).

A more recent development is recombinant vaccines, which involve genetically engineering a less harmful virus so that it includes a small part of the target virus. Our body launches an immune response to the carrier virus, but also to the target virus.

Over the past few years, this approach has been used to develop a vaccine (called rVSV-ZEBOV) against the Ebola virus. It consists of a vesicular stomatitis animal virus (which causes flu-like symptoms in humans), engineered to have an outer protein of the Zaire strain of Ebola.

Vaccines go through a huge amount of testing to check that they are safe and effective, whether there are any side effects, and what dosage levels are suitable. It usually takes years before a vaccine is commercially available.

Sometimes this is too long, and the new Ebola vaccine is being administered under ‘compassionate use’ terms: it has yet to complete all its formal testing and paperwork, but has been shown to be safe and effective. Something similar may be possible if one of the many groups around the world working on a vaccine for the new strain of coronavirus (SARS-CoV-2) is successful.

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Amy ArthurEditorial Assistant, BBC Science Focus

Amy is the Editorial Assistant at BBC Science Focus. Her BA degree specialised in science publishing and she has been working as a journalist since graduating in 2018. In 2020, Amy was named Editorial Assistant of the Year by the British Society of Magazine Editors. She looks after all things books, culture and media. Her interests range from natural history and wildlife, to women in STEM and accessibility tech.