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Research shows that Covid-19 antibodies weaken over time, suggesting that immunity may disappear

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LONDON – A large English study shows that the number of people with Covid-19 antibodies decreases significantly in the summer, suggesting that infection with the virus may not provide long-term immunity from future infection.

A study of 365,000 adults in England who were tested at home using a finger prick test showed that the proportion of people who tested positive for Covid-1

9 antibodies fell by 26.5% between June 20 and 12. weeks after the peak of infections in the country – and September 28.

The results also suggest that people who show no symptoms are more likely to lose detectable antibodies before those who show symptoms. The study, conducted by Imperial College London and the electoral organization Ipsos Mori, was funded by the British government, which announced the results and published the study on Monday night. The results have not yet been reviewed by other experts.

Doctors do not yet know whether the antibodies provide effective immunity against Covid-19 reinfection. But even if they do, and the results of this study are confirmed, it suggests that it is difficult to achieve the prospect of widespread long-term immune immunity against the virus. Herd immunity occurs when enough people in a population develop an immune response, either through a previous infection or vaccination, so that the virus cannot spread easily and even those who are not immunized have protection.

The findings show that 18-24-year-olds lose antibodies more slowly than those over 75 years of age. The smallest decrease of 14.9% is in people aged between 18 and 24 years, and the largest decrease of 29% is in people over 75 years of age.

The study reflects earlier smaller studies and suggests that antibodies to the virus decrease for 6-12 months after infection, as with other seasonal coronaviruses such as the common cold. The study does not show whether other types of immune responses – such as those contributed by so-called T cells – would help prevent reinfection.

The study shows that 6% of the population of England have antibodies on June 20, compared to 4.4% on September 28. At the end of September, 9% of people showed antibodies in London, compared to just 1.6% in the least affected region in the south-west of England.

Among ethnic groups, 13.8% of blacks were tested for antibodies in late September and 9.7% of Asians, mostly South Asians. This compared to 3.6% of white people. The ethnic groups of minorities in Britain, as well as in the United States, suffer disproportionately from the virus.

The authors acknowledged that the process has limitations. “It included non-overlapping random samples from the population, but people who have been exposed to the virus may be less likely to participate over time, which may have contributed to an apparent reduction in population antibodies,” they said. .

Write to Stephen Fiedler at stephen.fidler@wsj.com

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