COVID-19 Antibodies Decline Over Time, Study Shows
A study of 365,000 people in England found evidence that anti-coronavirus antibodies decrease over a 3-month period.
Participants performed three rounds of home needle stick tests between June 20 and September 28, according to a press release from Imperial College London. Rather than boosting immunity, the number of people with antibodies dropped from 6% at the start of the study to 4.4% at the end – a drop of about 26.5%, the statement said.
The decline was greatest among those aged 75 and over and lowest among those aged 18 to 24. Health workers showed no drop in antibodies.
“This very large study has shown that the proportion of people with detectable antibodies decreases over time,” said Professor Helen Ward, one of the report’s lead authors. “We don’t yet know if this will put these people at risk of re-infection with the virus that causes COVID-19, but it is essential that everyone continue to follow the guidelines to reduce the risk to themselves and to others.
The researchers warned, however, that the study had limitations and that the same groups of people weren’t necessarily tested every round, so there may be a chance that less infected people were tested every round.
The results are a blow to scientists who believe herd immunity will eventually bring down the coronavirus.
Herd immunity occurs when a large portion of a population becomes immune to a disease by developing antibodies, either through vaccination or infection.
While not every individual is immune, the group as a whole has protection. The researchers said 50-67% of the population should be resistant before the herd’s immunity kicks in and infection rates start to drop.
Professor Paul Elliott, program director at Imperial College London, pointed out that scientists still do not know to what extent – if at all – immunity is conferred by possession of COVID antibodies.
“A positive antibody test does not mean you are immune to COVID-19,” he said. “We still don’t know what level of immunity antibodies provide, nor how long that immunity lasts. If a person tests positive for antibodies, they should still follow national guidelines, including social distancing measures, take a swab test if they have symptoms, and wear headgear if necessary. “
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