Study predicting herd immunity in the UK from Monday called into question

Experts have questioned the validity of a new study that suggests Britain will pass the threshold for herd immunity from coronavirus next week.

According to modelling by University College London (UCL), the number of people in the country who have protection against Covid from either the vaccine or previous infection will hit 73.4% on 12 April.

Previous modelling from Imperial college suggested her immunity protection would stand at 34% by the end of March, the Daily Telegraph reported.

Figures from the Office for National Statistics (ONS) showed that some 54% of people in England already had coronavirus antibodies on 14 March.

Over 7 million people have been given a first dose of the vaccine since then, while antibodies from other coronaviruses has also increased the population level of immunity, the study said.

Should the country reach the threshold for herd immunity, it would spark pressure on the government to speed up the easing of lockdown restrictions in the coming weeks and months.

However, some scientists have said the research “does not appear to be internally consistent”.

Dr Louise Dyson, associate professor in epidemiology at the University of Warwick, said that the threshold level is based on what wold happen if the country returned to pre-pandemic contact rates – but the government’s roadmap does not allow for any immediate return to normal.

Christl Donnelly, professor of statistical epidemiology at Imperial College London, argued that social distancing meant that herd immunity “is not imminent”.

She added: “This is a conclusion that can be drawn directly from the R estimate obtained from the 10th round of REACT.

“It does not require any assumptions to be made about population immunity other than that it will not have changed dramatically between mid/late March and early April.”

Dr Adam Kucharski, associate professor in infectious disease epidemiology at the London School of Hygiene and Tropical Medicine, said that the modelling approach used in the UCL study “has a history of making over-confident and over-optimistic predictions”.

Despite over 31 million adults being given at least one dose of the vaccine, Kucharski argued that there is “a lot of uncertainty about vaccine effectiveness on reducing transmission”, as well as uncertainties about how the government will deal with future variants.

He said: “It is not clear from the online model description how it incorporates these uncertainties…

“Models can be a useful tool for exploring potential dynamics under different assumptions about transmission and control measures, but it's crucial that these assumptions are made clear, and known biases in past model performance are addressed before new results are publicised.”

Speaking in support of the herd immunity study, professor Karl Friston, of UCL, said: "The herd immunity estimates surprised me.

“However, they are unremarkable when one considers that over 50% of adults have been vaccinated, around 42% people have now been exposed to the virus and about 10% have pre-existing immunity.”

The model also suggests that the herd immunity threshold will drop to around 40% by the middle of summer, with no surge in infections predicted.

This goes against warnings from government scientists, who have predicted a third wave over summer as restrictions on social mixing leading up to it reduce.

However, Boris Johnson said he plans to stick “like glue” to his plan for easing restrictions despite the dire warnings.

Johnson, setting out the move to the second step of the road map on 12 April, said the shift was “fully justified by the data” and that he had seen “nothing” to make him think he would have to “deviate” from his intention to scrap all restrictions by 21 June at the earliest.

Watch: How England will leave lockdown