A new study by a team of researchers at the Imperial College London has found that antibodies developed following coronavirus infections disappear within a matter of weeks.
According to the REACT-2 study, antibody positivity fell by 26% between June and September.
While about 6% of those tested in July had detectable levels of coronavirus antibodies, only 4.4% had detectable levels of antibodies in September.
One of the researchers, Professor Helen Ward, said the study suggests that immunity “is waning quite rapidly.”
“We're only three months after our first [round of tests] and we're already showing a 26% decline in antibodies," Ward continued, according to a report by the BBC.
The researchers acknowledged that antibodies are just one form of immunity developed by the body.
White blood cells known as lymphocytes, including B cells and T cells, are also central to the human immune system.
Nevertheless, Prof. Wendy Barclay, one of the researchers, suggested that the decline in antibodies also points to a likely decline in overall immunity.
"On the balance of evidence, I would say it would look as if immunity declines away at the same rate as antibodies decline away, and that this is an indication of waning immunity."
Other studies have also suggested that antibody levels decline significantly within two to three months after coronavirus infections.
However, they suggest that the decline in antibodies does not imply a decline in long-term immunity, citing the formation of memory T and B cells. An August 2020 study even found that patients who had suffered only mild cases of the virus developed memory T and B cells, suggesting they had developed long-term immunity.
One October, 2020 study Sekine et al. not only found that coronavirus infections elicit functional memory T cells that protect against recurrent episodes, but also suggested that most asymptomatic individuals exposed to the virus had developed T cells.
Professor Paul Elliot, director of the REACT-2 study, said that despite his group’s findings, a vaccine against the coronavirus still could be useful in combatting the pandemic, speculating that it might provide longer-term protection than natural immunity following infections.
"The vaccine response may behave differently to the response to natural infection,” said Elliot.
Studies of the seasonal flu, however, suggest that vaccine immunity tends to wane even more rapidly than natural immunity caused by infection.
A February 2011 study of the 2009 H1N1 flu virus, for example, found that while over half of patients who had been infected with the virus had measurable levels of antibodies six months after being infected, just one third of vaccinated subjects also had.
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