Britain won’t achieve herd immunity with the current coronavirus vaccines even if every single Briton is injected, a study claimed today as SAGE scientists warned the draconian lockdown will need to stay in place until May.

Analysis from the University of East Anglia (UEA) found that the efficacy of current vaccines, combined with the emergence of new, more infectious variants of the virus, meant keeping the R below one without lockdown restrictions could become impossible.

UEA researchers say that even if every man, woman and child in the UK gets the Oxford jab it would only bring the R — the average number of people each patient infects — down to 1.3. But, because this vaccine is approved for over-18s only, the R would remain at about two when curbs are lifted.

The study found Pfizer’s jab – which is more effective at blocking coronavirus than the Oxford one – is capable of bringing the R below one and achieving herd immunity but it would require inoculating teenagers. Currently the jab is only approved for over-16s. Researchers warned it would ‘likely be impossible’ to hit the 82 per cent target needed because ‘people will refuse the vaccine’.

Scientists have always known eradicating Covid was an impossible task and the goal of the vaccine programme is not to prevent all transmission from occurring. Herd immunity occurs when enough of the population is immune to an infectious disease, preventing it from spreading.

Instead, the UK’s scheme is aimed at preventing the most vulnerable from dying or falling sick and piling pressure on the NHS. It’s hoped that once all vulnerable groups are immunised, the disease will become more manageable and restrictions can be gradually lifted.

But scientists on the Government’s Scientific Advisory Group for Emergencies (SAGE) warned today that the strict shutdown will need to remain in place until at least May because of the current pace of the vaccine rollout. Boris Johnson has promised to consider easing restrictions in mid-February once the 14million most vulnerable people have been given their first dose of the jabs.

But SAGE scientists who have modelled the rollout say easing restrictions next month has the ‘potential’ to cause a bigger epidemic than the one now because the single dose will only provide weak protection.They warned today that with huge community transmission and an NHS on the brink of being overwhelmed, loosening lockdown even slightly next month would lead to an ‘unsustainable’ situation.

Professor Matt Keeling, an epidemiologist from the University of Warwick, said: ‘I certainly don’t want individuals going to bars and restaurants on the 16th . If we’ve given people their first dose by February 15, that’s not going to give that much protection.’ He warned the most ‘optimistic’ outcome would be for ‘some’ restrictions to be lifted in May.

Dr Marc Baguelin, an infectious disease expert at Imperial College London who was also involved in the modelling, claimed that easing lockdown before then would cause a spike ‘that is really bad’.

Pictured, the impact on R rate for various vaccination scenarios, herd immunity is only achieved if R is kept below 1. The green line shows the Pfizer vaccine, and the blue line shows the effectiveness of Oxford’s vaccine according to the 70.4% effectiveness claimed in data sent to MHRA. The red line shows data from phase 3 clinical trials for two standards dose jabs of the Oxford jab against both symptomatic and asymptomatic infection

Lifting lockdown completely before spring could lead to up to 6,000 daily Covid deaths, depending on how good the vaccines are at stopping transmission, something scientists won’t know for months when more studies are completed. But the SAGE scientists who did the modelling stressed these were imperfect models based on lots of variables and should not be interpreted as predictions

SAGE scientists Professor Mark Woolhouse, Professor Matt Keeling and Dr Marc Baguelin, as well as Imperial College London infectious diseases expert Dr Anne Cori. The four scientists modelled how Britain’s epidemic will change during the vaccine rollout