Immunity of those with covid-19 “decreases very quickly”, says new study

A British study found that the immunity acquired by people who were infected with the new coronavirus “decreases very quickly”, especially in asymptomatic patients, and can only last for 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 against covid-19. “During this period, the proportion 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 after infection.” “Immunity declines quickly,” said Helen Ward, professor of public health at Imperial College London.

In a first phase, the researchers found that between late June and early July, about 60 in every 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 the antibodies. These data suggest that the number of people with antibodies decreased by more than a quarter between summer and autumn.

The study also shows that “people who did not experience covid-19-related symptoms are likely to lose their detectable antibodies more quickly than those who experienced the symptoms.”

We can be “reinfected” by seasonal coronaviruses

The proportion of antibodies in people who tested positive for the virus decreased by 22.3% over the three months, when this reduction reached 64% in those who did not report having been affected by covid-19. All age groups are affected by this decline in immunity, but mainly the elderly: between June and September, the proportion 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 to 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,” said the researchers, emphasizing the importance of continuing to comply with health guidelines.

Virologist Wendy Barclay of Imperial College London explained that “this new 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 can be “reinfected every year or every two years” by these seasonal coronaviruses due to declining immunity, he stressed in statements to the “Radio Times”.

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