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A study of 365,000 people in England found evidence that coronavirus antibodies decrease over a 3-month period.
Participants performed three rounds of fingerstick tests at home between June 20 and September 28, according to a press release from Imperial College London. Instead of developing immunity, the number of people with antibodies dropped from 6% at the beginning of the study to 4.4% at the end, a drop of about 26.5%, according to the statement.
The decline was greatest among people 75 and older and lowest among people 18 to 24 years old. Health workers showed no decrease in antibodies.
“This large study has shown that the proportion of people with detectable antibodies is decreasing over time,” said Professor Helen Ward, one of the report’s lead authors. “We do not yet know if this will leave these people at risk of reinfection with the virus that causes COVID-19, but it is essential that everyone follow the guidelines to reduce the risk to themselves and others.”
The researchers cautioned, however, that the study has limitations and that the same groups of people were not necessarily tested in each round, so there may be a possibility that fewer infected people were tested in each round.
The findings are a blow to scientists who believe herd immunity will eventually reduce the coronavirus.
Herd immunity occurs when a large part of the population becomes immune to a disease by developing antibodies, either through vaccination or infection.
While all individuals may not be immune, the group as a whole has protection. Researchers have said that between 50% and 67% of the population would need to be resistant before herd immunity kicks in and infection rates begin to decline.
Professor Paul Elliott, program director at Imperial College London, stressed that scientists do not yet know how much immunity, if any, is imparted by having COVID antibodies.
“A positive antibody test does not mean that you are immune to COVID-19,” he said. “It is not clear what level of immunity the antibodies provide, or how long this immunity lasts. If someone tests positive for antibodies, they should still follow national guidelines, including social distancing measures, get a swab test if they have symptoms, and wear face covers when necessary. “
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