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A British study found that the immunity acquired by people who had the new coronavirus “wanes very quickly”, 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, regularly testing them for antibodies to 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 the infection”.
“Immunity declines rapidly,” 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 out of every 1,000 people had detectable antibodies.
But in the tests carried out in September the value was already quite different: only 44 out of every thousand people had the antibodies.
These data suggest that the number of people with antibodies has decreased by more than a quarter between summer and fall.
The study also shows that “people who did not experience symptoms related to COVID-19 will likely lose their detectable antibodies more quickly than those who did experience symptoms.”
The proportion of antibodies in people who tested positive for the virus decreased by 22.3% during the three months, when this reduction reached 64% in those who did not report having been affected by covid-19.
If all age groups are affected by this decrease in immunity, but mainly the elderly: between June and September, the proportion of people older than 75 years with antibodies decreased by 39%, when for young people between 18 and 24 years 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 the antibodies confer an effective level of immunity or, if such immunity exists, how long it lasts,” the researchers said, emphasizing the importance of continuing to adhere to health guidelines.
Virologist Wendy Barclay of Imperial College London explained that “this new coronavirus appears to behave quite similarly to 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 decreased immunity, he said in a statement to the Radio Times.
Faced with a possible risk of reinfection by the new coronavirus, the professor is not in favor of the concept of “immunity passports”, which aims to allow people cured of the new coronavirus to lead a normal life.
“At the moment, this is not a good idea because the quality of the antibody response can vary from one individual to another,” said Professor Barclay.
The virologist also said “be optimistic about vaccines because vaccines work differently” and can confer longer immunity.
The SARS-CoV-2 pandemic has killed at least 1,160,768 people worldwide since the disease was identified in late December, according to data compiled today by the AFP news agency from official sources.
In Portugal, 2,343 people died from 121,133 confirmed cases of infection, according to the most recent bulletin from the Directorate General of Health.
The disease is transmitted by a new coronavirus detected at the end of December 2019 in Wuhan, a city in central China.
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