According to experts, coronavirus antibodies can protect against reinfection even if they weaken over time, who say people should not be alarmed by recent studies whose results appear to be left behind. opposite.
Antibodies and other immune responses are the main focus of coronavirus research because of the important implications for how long humans can be protected before a vaccine becomes available. For example, if antibodies induce permanent immunity, those already infected may be protected until a viable vaccine is available. But weakened antibodies could mean that Covid-19 survivors could be at risk of reinfection.
A pair of studies published this week sparked some confusion because of their differing findings. An article published in Science, led by scientists in New York, found that the Covid-19 antibodies developed by the immune system remained at a steady level for about 5 months. But two days earlier, an earlier study that had yet to be reviewed, found that out of hundreds of thousands of participants across the UK, antibody levels dropped rapidly, dropping more than 26% between period of three months.
Most experts agree that antibody levels decrease over time and that these declines are completely unrelated.
Ritesh Tandon, associate professor of microbiology and immunology at the University of Mississippi Medical Center, said: “If you think about basic immunology, you should have an antibody response first and then that antibody response will disappear. learn. “Antibodies are dynamic – they are not made once and are in the blood.”
Dr. Anthony Fauci, the nation’s leading infectious disease specialist, echoed that view, adding that the reduced amount of antibody doesn’t necessarily translate into a lack of immunity.
“Just because antibody levels drop, that doesn’t mean you lose your protection,” he said Thursday during a press conference from the National Institutes of Health.
In a recent study published in Science, researchers at the Icahn School of Medicine in Mount Sinai used a database of immune responses from 30,000 New Yorkers who tested positive for coronavirus from March to October and follow up with 121 volunteers from time to time.
The researchers found that the antibody response peaked about two to three months after infection. Dr Ania Wajnberg, associate professor of medicine at the Icahn School of Medicine and co-author of the Mount Sinai study, said that 90% of those who have recovered, the antibody levels then drop but remain stable around 5 month.
“Most patients have a relatively strong reaction and until now it has persisted over time,” she said.
In a UK study, scientists at Imperial College London found that the prevalence of antibody in British participants dropped from 6% around the end of June to 4.4. % in September. And using home trials distributed to more than 365,000 people, researchers observed antibody levels decreased by more than 26% over three months.
But there are limitations to 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 failed to accurately measure antibody levels.
“The sensitivity between the two trials is a big difference,” said Alan Wu, professor of laboratory medicine at the University of California, San Francisco, who was not involved in both studies. “It’s a little apple and orange, in the sense that the studies aren’t done the same way.”
But despite seemingly different results from the two studies, both may be correct, says Dr. Arturo Casadevall, dean of the department of molecular microbiology and immunology at the Johns Hopkins Bloomberg School of Public Health. There is nothing unreasonable – or particularly alarming – if the level of antibodies drops rapidly after one recovers and then persists for a while at a much lower level, he said.
“We know that other coronaviruses tend to induce non-permanent immunity,” said Casadevall. “The question is: How much antibody do you need to prevent reinfection? It may be that you need very little. “
However, antibodies are not the only weapon in the immune system’s arsenal. There are cellular immune responses that can recognize the virus and provide some protective immunity. People who have been infected with the virus also often create “memory cells” that can recall certain pathogens and quickly mobilize defenses against reinfection.
“Antibody immunity is just one part of immunity,” said Casadevall. “If you have an immune memory, which means if you go up against the coronavirus, your body doesn’t need two weeks to figure out how to respond. That memory can appear immediately. “
According to Tandon, there is no easy way to detect memory cells and cellular immune responses in restored patients, but it is an active area of research. And to date, the immune responses to coronavirus are more or less consistent with other known coronaviruses, he added.
“It works according to the rules of immunology – it’s not an alien virus that we don’t seem to know about,” Tandon said. “I haven’t seen anything that makes me think this is a virus very different from anything we’ve seen before.”