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Immunity to coronavirus may last more than six months, study suggests

What would immunity from covid-19 give us? 1:35

. – Preliminary research suggests that immunity to the coronavirus that causes COVID-19 can last for at least six months, and possibly much longer, perhaps even years, when all components of the body’s immune memory are taken into consideration.

The document, published on Monday on the online server biorxiv.org, adds to the investigations into immunity to the new coronavirus. Several studies have focused on antibodies or protein components of the immune system, and some have suggested that immunity might wane within a few months.

However, the new study, which has not been peer-reviewed or published in a scientific journal, involves analyzing multiple compartments of immunological memory over time: antibodies, B cells and T cells, among other characteristics of immune memory. .

The study included 185 adults, ages 19 to 81, in the United States who had recovered from COVID-19. Most of the adults had a mild illness.

Researchers, from the La Jolla Institute for Immunology, the University of California, San Diego and the Icahn School of Medicine at Mount Sinai, analyzed blood samples collected at various points after the onset of symptoms, and some collected more than six months after.

Immunological memory against coronavirus

In the blood samples, the researchers examined components of immune memory. They found that the antibodies “were durable” with only “modest drops” appearing between six and eight months, but found that there was a 200-fold range in the level of antibody responses among adults.

The researchers also found that memory B cells were detected in almost all COVID-19 cases, and there appeared to be an increase in memory B cells over time. “B-cell memory for some other infections has been shown to be long-lasting, including more than 60 years after smallpox vaccination or more than 90 years after influenza infection,” the researchers wrote in their study.

The researchers identified two types of T cells, and their data suggests that “T cell memory may reach a more stable plateau, or slower decline phase, beyond the first 6 months after infection,” they wrote.

Study with limitations

The study has limitations, including the fact that more research is needed to determine whether similar findings would emerge among a larger group of people at more points in time.

“Overall, this is an important study confirming the existence of memory immune to SARS-CoV-2, but with a degree of variation from person to person,” said Lawrence Young, professor of molecular oncology at the University of Warwick, in a statement distributed by the UK-based Science Media Center on Wednesday. SARS-CoV-2 is the name of the new coronavirus.

‘This variation could be because some people have had a very low-level asymptomatic infection. Previously infected people with a low immune memory response might be expected to be susceptible to re-infection with SARS-CoV-2, ”said Young, who was not involved in the new study.

“But the important take-home message is that the immune response to the virus is more durable than previously thought, and this allows us to remain hopeful that an effective vaccine can induce sustained protective immunity.”

It remains to be seen how much more durable than previously thought.

What about other viruses?

When it comes to other viruses, a measles attack usually leaves someone immune for life, an effect known as sterilizing immunity. The same happened with smallpox, before the virus was eradicated in the 1970s through a worldwide vaccination campaign. And proper vaccination against measles and smallpox fully protects against infection.

But respiratory viruses like influenza are more complicated. People can get the flu over and over again, and flu vaccines generally provide only partial protection against serious infections and illnesses. Part of that is due to the flu’s tendency to mutate.

Coronaviruses seem to be in the middle. There are seven known coronaviruses that can infect people, and SARS-CoV-2 is just one of them. Many human coronaviruses can cause the common cold, but since they are not usually fatal, they have not been studied as well.

CNN’s Maggie Fox contributed to this report.