Why antibodies to Coronavirus fade quickly in asymptomatic people, says Study

*Does everyone infected with the virus produce antibodies — and if so, how long do they last? Ask scientists

Isola Moses | ConsumerConnect

You may have antibodies after novel Coronavirus (COVID-19) infection, but not for long, say scientists in a new study.

It’s a question that has haunted scientists since the deadly pandemic began: Does everyone infected with the virus produce antibodies — and if so, how long do they last?

Not very long, suggests a new study published Thursday, June 18, 2020, in Nature Medicine, reports The New York Times.

What are antibodies?

They are protective proteins made in response to an infection, which may last only two to three months, especially in people who never showed symptoms while they were infected.

However, the conclusion does not necessarily mean that these people can be infected a second time, several experts have cautioned.

Even low levels of powerful neutralising antibodies may still be protective, as are the immune system’s T cells and B cells.

Report says that the results yet offer a strong note of caution against the idea of “immunity certificates” for people who have recovered from the illness, the authors suggested.

Antibodies to other Coronaviruses, including those that cause SARS and MERS, are thought to last about a year.

Scientists had hoped that antibodies to the new virus might last at least as long.

Several studies have now shown that most people who are visibly ill with Covid-19 develop antibodies to the virus, although it has been unclear how long those antibodies last, according to the report.

The new study is the first to characterise the immune response in asymptomatic people.

In the study, the researchers compared 37 asymptomatic people to an equal number who had symptoms in the Wanzhou District of China.

The investigators found that asymptomatic people mount a weaker response to the virus than those who develop symptoms.

Antibody levels fell to undetectable levels in 40 percent of asymptomatic people, compared with just 13 percent of symptomatic people.

The sample size is small, however, and the researchers did not take into account protection offered by immune cells that may fight the virus on their own or make new antibodies when the virus invades.

A few studies have shown that the coronavirus stimulates a robust and protective cellular immune response.

Angela Rasmussen, a virologist at Columbia University, said: “Most people are generally not aware of T cell immunity, and so much of the conversation has focused on antibody levels.”

Apart from T cells, which can kill the virus on encounter, people who have been infected make so-called memory B cells, which can rapidly ramp up antibody production when needed.

Florian Krammer, a virologist at the Icahn School of Medicine at Mount Sinai, who has led several studies of antibodies to the Coronavirus, stated: “If they find the virus again, they remember and start to make antibodies very, very quickly.”

Antibodies to one viral protein dropped below detectable levels, according to the study. But a second set of antibodies targeting the so-called spike protein of the coronavirus — needed to neutralise the virus and prevent reinfection — were still present.

In fact, these antibodies seemed to show a smaller decline in asymptomatic people than in symptomatic people.

“The neutralising antibody is what matters, and that tells a very different story,” Dr. Krammer said.

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