A British study found that the immunity acquired by people who have been infected with the new coronavirus “declines very rapidly”, especially in asymptomatic patients, and can only last a few months.
From June 20 to September 28, Imperial College London and the Ipsos Mori Institute followed 350,000 randomly selected people in England, testing them regularly to see if they had antibodies to covid-19. “During this period, the percentage of people who tested positive for covid-19 antibodies decreased by 26.5%,” which, according to the study, “suggests a reduction in antibodies in the weeks or months following infection.” . “Immunity drops rapidly,” said Helen Ward, a professor of public health at Imperial College London.
In a first phase, the researchers found that between the end of June and the beginning of July, about 60 in a thousand people had detectable antibodies. But in the tests carried out in September the value was already quite different: only 44 per thousand people had antibodies. These data suggest that the number of people with antibodies decreased by more than a quarter between the summer and fall.
The study also shows that “people who have not experienced covid-19-related symptoms are likely to lose their detectable antibodies more quickly than those who have experienced symptoms.”
We can be “reinfected” by seasonal coronaviruses
The percentage of antibodies in people who tested positive for the virus decreased by 22.3% in the three months, when this reduction reached 64% in those who did not report having covid-19. All age groups are affected by this drop in immunity, but mainly the elderly: between June and September the percentage of people over 75 with antibodies decreased by 39%, while for young people between 18 and 24 the reduction was 14.9%.
“This study is a crucial part of the research, helping us understand how covid-19 antibodies evolve over time,” said Secretary of State for Health James Bethell. However, “it is not yet known whether antibodies confer an effective level of immunity or, if such immunity exists, how long it lasts,” the researchers said, stressing the importance of continuing to adhere to health guidelines.
Virologist Wendy Barclay of Imperial College London explained that “this novel coronavirus appears to behave quite similarly to the seasonal coronaviruses that have existed in humans for decades, if not hundreds of thousands of years.” We may be “reinfected every year or every two years” by these seasonal coronaviruses due to the drop in immunity, he pointed out in statements to “Radio Times”.