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Covid-19 antibodies diminish over time, but experts say there is no reason to worry

Coronavirus antibodies can provide protection against reinfections, though they diminish over time, according to experts, who say people should not be worried about recent studies that appear to have conflicting results.

Antibodies and other immune responses have been a major focus in coronavirus research because there are important implications for how long people could be protected before a vaccine is available. For example, if antibodies confer long-lasting immunity, people who are infected can be protected until there is a viable vaccine. However, decreasing antibodies may mean that Covid-1

9 survivors may be at risk for reinfection.

A few studies released this week raised some confusion due to their divergent findings. A paper published in the journal Science, led by researchers in New York, found that Covid-19 antibodies developed by the immune system lingered at stable levels for about five months. But two days earlier, a peer-reviewed peer-reviewed study found that among hundreds of thousands of participants across the UK, antibody levels dropped rapidly, falling more than 26 percent over a three-month period.

Most experts agree that antibody levels decrease over time and that these decreases are not entirely relevant.

“If you think about basic immunology, you should initially have an antibody response, and then the antibody response should disappear,” said Ritesh Tandon, an associate professor of microbiology and immunology at the University of Mississippi Medical Center who was not involved in any of the research. “Antibodies are dynamic – they are not even produced and remain in the blood.”

Dr. Anthony Fauci, the nation’s leading expert on infectious diseases, reiterated this sentiment, adding that declining antibody levels do not necessarily translate into a lack of immunity.

“Just because the level of antibodies decreases does not mean you lose protection,” he said Thursday in a press briefing from the National Institutes of Health.

In a recent study published in Science, researchers at the Icahn School of Medicine on Mount Sinai used a database of immune responses from 30,000 New Yorkers who tested positive for coronavirus between March and October and monitored 121 volunteers over time.

The researchers found that antibody responses peaked approximately two to three months after infection. And in 90 percent of the people who recovered, antibody levels subsequently dropped but remained stable for about five months, Dr. Ania Wajnberg, associate professor of medicine at the Icahn School of Medicine and co-author of the Mount Sinai study.

“A majority of patients have a relatively robust response, and so far it is persistent over time,” she said.

In the UK study, researchers at Imperial College London found that antibody prevalence among UK participants dropped from 6 per cent in late June to 4.4 per cent in September. And using home tests distributed to more than 365,000 people, the researchers observed a drop of more than 26 percent in antibody levels over three months.

But there were limitations with the British study. Although the study had hundreds of thousands of participants, the researchers did not follow the same people over time. The study also did not accurately measure antibody levels.

“The sensitivity between the two tests is a big difference,” said Alan Wu, a professor of laboratory medicine at the University of California, San Francisco, who was not involved in any of the studies. “It’s a bit of apples and oranges in the sense that the studies are not carried out in the same way.”

But despite the seemingly divergent results from the two studies, they can both be true, according to Dr. Arturo Casadevall, Chair of the Department of Molecular Microbiology and Immunology at the Johns Hopkins Bloomberg School of Public Health. It is not unreasonable – or particularly alarming – if antibody levels fall rapidly after a person recovers and then persists for a while at a much lower level, he said.

“We know that other coronaviruses tend to elicit immunity that is not long-lasting,” Casadevall said. The question is: How much antibodies do you need to prevent reinfection? You may need very little. ”

Antibodies are still not the only weapons in the immune system’s arsenal. There are cellular immune responses that can recognize a virus and confer some protective immunity. People who have been infected with a virus typically also produce “memory cells” that can recall certain pathogens and quickly mobilize a defense against reinfection.

“Antibody immunity is only part of the immunity,” Casadevall said. “If you have immunological memory, it means that if you confront the coronavirus again, your body does not need two weeks to figure out how to react. That memory could kick in right away. ”

There is no easy way to detect memory cells and cellular immune responses in recovering patients, but it is an active area of ​​research, according to Tandon. And so far, immune responses to coronavirus are more or less in line with other known coronaviruses, he added.

“It plays by the rules of immunology – it’s not a foreign virus that we apparently know nothing about,” Tandon said. “I have not seen anything that makes me believe that this is a virus that is very different from anything we have seen before.”

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