New study suggests COVID-19 immunity is 'waning,' researchers say

Antibodies would be expected to decline over time, as they do with other coronaviruses, like the common cold, but how fast and how far they fall is unknown for Covid-19.

The federal government is investing $1.9 million for a national study of COVID-19 antibodies that is targeted specifically at some of the more high-risk populations in the country.

Imperial College London Department of Infectious Disease head, Wendy Barclay, told reporters in London they are confident in what a decline in antibodies tells them.

While the number of people testing positive for antibodies declined gradually in the population regardless of employment type, the number of healthcare workers testing positive for antibodies didn't change over time.

According to a recent study carried out by researchers at the Imperial College London, the proportion of people in Britain with antibodies that protect against COVID-19 declined over the summer, adding to evidence that natural immunity can wane in a matter of months.

However, "it is not yet known whether the antibodies confer an effective level of immunity or, if such immunity exists, how long it lasts", specified the researchers, stressing the importance of continuing to respect the sanitary instructions.

The study involved 365,000 randomly-selected adults administering at home three rounds of finger prick tests for coronavirus antibodies between June 20 and September 28.

The proportion of antibodies in people who tested positive for the virus decreased by 22.3% over the three months, when this decrease reached 64% in those who had not declared having been reached by Covid-19.

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A study conducted in the United Kingdom found that during the summer, antibodies against the novel coronavirus rapidly declined in the British population, a report by Reuters revealed.

This is down from 6% from studies taken in June, and 4.8% from studies taken in August. Among those aged 75 and above, antibody levels fell by 39pc, while a drop of just 15pc was seen in those aged between 18 and 24.

"This very large study has shown that the proportion of people with detectable antibodies is falling over time". IgG are one type, but the tests were not created to detect other types of antibodies.

There was a steeper decline in those over 65 and in those who were asymptomatic compared with those who had symptoms. Based on their experience with other coronaviruses, the scientists suggest immunity may not be long-lasting, reports CBC Canada.

This study has ominous implications for those who believe the pandemic can be brought to heel through herd immunity.

"We don't yet know whether this will leave these people at risk of reinfection with the virus that causes COVID-19, but it is essential that everyone continues to follow guidance to reduce the risk to themselves and others", Professor Helen Ward, one of the lead authors of the report.

"What we do know is that seasonal coronaviruses that circulate every year can reinfect people after six to 12 months and we suspect that the way the body reacts to these coronaviruses is similar".