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Yet the new study, which has not been peer reviewed or published in a scientific journal, involves analyzing several compartments of immune memory over time: antibodies, B cells, and T cells, among other features of the immune system. immune memory.
The study included 185 adults, aged 19 to 81, in the United States who had recovered from Covid-19. Most of the adults had mild illness.
The researchers – from the La Jolla Institute for Immunology, the University of California at San Diego, and the Icahn School of Medicine at Mount Sinai – analyzed blood samples taken at various points after symptoms appeared. , some collected more than six months later. .
In the blood samples, the researchers looked at the components of immune memory. They found that the antibodies “were durable” with only “modest declines” emerging at six to eight months, but noted that there was an approximately 200-fold range in the level of antibody responses in adults. .
The researchers also found that memory B cells were detected in almost all cases of Covid-19 and that there appeared to be an increase in memory B cells over time. “B-cell memory of some other infections has been observed to be long lasting, including more than 60 years after vaccination against smallpox, or 90 years after infection with influenza,” the researchers wrote in their report. study.
The researchers identified two types of T cells and their data suggests that “T cell memory may reach a more stable plateau, or a slower decay phase, later than the first 6 months after infection,” they said. they wrote.
The study has limitations, including the fact that more research is needed to determine whether similar results would emerge in a larger group of people at multiple times.
“This variation could be due to the fact that some people have had a very low level asymptomatic infection. One would expect that people previously infected with a weak immune response from memory are likely to be reinfected 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 continue to hope that an effective vaccine will be able to induce long-lasting protective immunity.”
It remains to be seen how much longer life than previously thought.
When it comes to other viruses, a measles episode usually leaves a person immune for life – an effect known as sterilizing immunity. The same was true for smallpox, before this virus was eradicated in the 1970s by a global vaccination campaign. And a good measles and smallpox vaccination completely protects against infection.
But respiratory viruses such as influenza are trickier. People can get the flu repeatedly, and flu shots usually provide only partial protection against serious illness and infection. This is in part due to the flu’s tendency to mutate.
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