Antibody data blow to herd immunity hope

Proportion of population with proteins preventing further infections found to be far lower than believed

THE proportion of the population with Covid-19 antibodies is up to a third lower than previously thought, according to official data.

Figures collated by Public Health England show that, in London, where the prevalence of antibodies is at its highest, only one in 10 people are now estimated to have them, compared with one in six following the peak of the outbreak in the UK.

In the North East, less than 5 per cent of people were found to have Covid-19 antibodies, the protective proteins produced to help fight off the virus. The data deals a further blow to the feasibility of “herd immunity” preventing a second wave of infections. The Government has also suggested that patients who recover from Covid-19 could be given “immunity passports” once scientists are about to prove that the antibodies provide a significant period of protection from a second infection.

But the low proportion of those testing positive for antibodies suggests that such a move would allow only small numbers of people to move around more freely.

The figures are based on samples taken from blood donors in different parts of the country.

PHE said the earlier figures had excluded samples from donors aged over 70, who had been banned from giving blood during the lockdown, when they were asked to stay at home. As a result, earlier figures showing the proportion of donors with antibodies appears to have given a misleading impression of the overall picture in the country.

The latest figures show that the overall proportion of people with antibodies is estimated at 6.5 per cent nationally in England. The highest prevalence was in London, where 9.9 per cent of blood donors were found to have antibodies, compared with 6.5 per cent in the Midlands and 4.7 per cent in the North East, down from an estimated 7.1 per cent earlier in the epidemic.

The data chime with the latest figures from the Office for National Statistics, which stated: “As of 29 June 2020, 6.3 per cent of individuals from whom blood samples were taken tested positive for antibodies.”

Addressing PHE’s advisory board last week, Yvonne Doyle, the body’s medical director, said: “We reckon that over the peak we had in London about 16 per cent of the population were showing that they had antibodies. This is dropping off now and it’s now much lower than that. Overall between six and 10 per cent of the population are showing those kind of antibodies, as we do our regular seroprevalence testing.”

Earlier this month, a study by scientists at King’s College London found that Covid-19 antibodies peaked three weeks after the onset of symptoms and then begin to fade. However, PHE said that, while “waning immunity” may be a “contributory factor” in the drop in the prevalence of antibodies, it was “likely to play a relatively small role in the overall trends observed to date”.

PHE said: “In more recent sampling periods, prevalence estimates are lower and this is likely to be largely driven by changes in the precise locations of sampling over time and potential demographic differences in the donor population as lockdown measures are relaxed.”

Some scientists have said that large numbers of the population may have natural immunity against coronavirus even if they have never been infected.

Earlier this month, Sir John Bell, Regius Professor of Medicine at Oxford University, who is leading a team to develop a vaccine, told The Telegraph that there was likely to be a “background level” of protection for a “significant number of people”. Recent studies have suggested the immune system can be primed by other coronaviruses, such as the common cold, giving the body a head start in fighting off Covid-19. Previous research has indicated that coronavirus antibodies may only last for a few months.

Earlier this month scientists from King’s College London analysed 90 patients and healthcare workers at Guy’s and St Thomas’ NHS Trust and found the level of antibodies in the immune system peaked three weeks after showing symptoms.

In the first longitudinal study of its kind, 60 per cent of participants were found to have a “potent” antibody response while in the throes of the virus, but this fell to 17 per cent after three months. Levels of antibodies depleted by as much as 23-fold in the threemonth period after infection and in some people became undetectable.

Researchers in Munich found that those who have recovered could be vulnerable to a second infection.