LONDON – A large English study has shown that the number of people carrying anti-Covid-19 antibodies declined significantly over the summer, suggesting the virus may not confer lasting immunity against future infection.
The survey of 365,000 adults in England who tested themselves at home using a finger prick test showed that the proportion of people who tested positive for Covid-19 antibodies decreased by 26.5% between June 20 – 12 weeks after the peak of infections in the country – and Sept.
The results also suggest that people who do not have symptoms are likely to lose detectable antibodies before those who do have symptoms. The study, conducted by Imperial College London and the Ipsos Mori polling organization, was funded by the UK government, which announced the results and published the study on Monday evening. The results have not yet been reviewed by other experts.
Doctors are not yet sure whether the antibodies confer effective immunity against re-infection with Covid-19. But even if it does and the results of this investigation are confirmed, it suggests that the prospect of long-term herd immunity to the virus will be difficult to realize. Herd immunity occurs when a sufficient number of people in a population develop an immune response, either through a previous infection or through vaccination, so that the virus cannot spread easily and even those who are not. not immune are protected.
The results showed that 18-24 year olds lost antibodies at a slower rate than those aged 75 and older. The smallest drop of 14.9% was among those aged 18 to 24, and the largest drop of 29% was among those aged 75 and over.
The study mirrors earlier smaller trials and suggests that antibodies to the virus decline 6 to 12 months after infection, as in other seasonal coronaviruses such as the common cold. The study does not indicate whether other types of immune responses – such as those made by so-called T cells – would help protect against reinfection.
The study showed that 6% of the population of England had antibodies on June 20, compared to 4.4% on September 28. At the end of September, 9% of people had antibodies in London, compared to only 1.6% in the least affected region. in the South West of England.
Among ethnic groups, 13.8% of blacks tested for antibodies in late September and 9.7% of Asians – mostly South Asians. This compared to 3.6% of whites. Minority ethnic groups in the UK, like the US, have suffered disproportionately from the virus.
The authors admitted that the trial had limitations. “It included non-overlapping random samples of the population, but it is possible that people who had been exposed to the virus were less likely to participate over time, which may have contributed to the apparent decrease in antibodies in the population.” , they said.
Write to Stephen Fidler at [email protected]