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Lasting Immunity Develops After Even Mild COVID-19 Infection, Studies Find

In some cases, immunity increased over three months.
Close-Up Of Gloved Hands Holding Syringe And Virus Representation
Adriana Duduleanu / EyeEm / Getty Images

Several new studies show that people who had even a mild coronavirus infection developed a lasting immunity to the virus.

The studies, none of which have yet been peer-reviewed, show that antibodies and immune cells known as B cells and T cells, which are able to recognize the SARS-CoV-2 virus, appear to be present months after infections have been cured.

One group of scientists “performed a longitudinal assessment of individuals recovered from mildly symptomatic COVID-19 to determine if they develop and sustain immunological memory against the virus,” their study says. “We found that recovered individuals developed SARS-CoV-2-specific IgG antibody and neutralizing plasma, as well as virus-specific memory B and T cells that not only persisted, but in some cases increased numerically over three months following symptom onset.”

“Furthermore, the SARS-CoV-2-specific memory lymphocytes exhibited characteristics associated with potent antiviral immunity: memory T cells secreted IFN-γ and expanded upon antigen re-encounter, while memory B cells expressed receptors capable of neutralizing virus when expressed as antibodies. These findings demonstrate that mild COVID-19 elicits memory lymphocytes that persist and display functional hallmarks associated with antiviral protective immunity,” the scientists wrote.

“This is exactly what you would hope for,” Marion Pepper, an immunologist at the University of Washington who co-authored the study told The New York Times. “All the pieces are there to have a totally protective immune response.”

Pepper said the next move will be more testing to find evidence that people are able to ward off the coronavirus after being exposed a second time, the paper reported.

“This is very promising,” Smita Iyer, an immunologist at the University of California, told the paper. “This calls for some optimism about herd immunity, and potentially a vaccine.”

Said the Times:

Research on the coronavirus is proceeding so quickly, and in such volume, that the traditional review process often cannot keep pace. For the studies discussed here — as with un-peer-reviewed studies in general — The Times arranged for several experts to read and evaluate them.

Although researchers cannot forecast how long these immune responses will last, many experts consider the data a welcome indication that the body has a good chance of fending off the coronavirus if exposed to it again. “Things are really working as they’re supposed to,” said Deepta Bhattacharya, an immunologist at the University of Arizona and an author on one of the new studies, which has not yet been peer reviewed.

The world’s largest COVID-19 vaccine study in the world began early this month, with the first of 30,000 Americans volunteering to take the shots. The experimental vaccine, developed by the National Institutes of Health (NIH) and Moderna Inc., is in phase three of the development process, which includes tests at clinical sites across the country.

“Having a safe and effective vaccine distributed by the end of 2020 is a stretch goal, but it’s the right goal for the American people,” NIH Director Dr. Francis Collins said in a statement. “The launch of this phase-3 trial in record time while maintaining the most stringent safety measures demonstrates American ingenuity at its best and what can be done when stakeholders come together with unassailable objectivity toward a common goal.”

Related: Russia Becomes First Nation To Approve COVID-19 Vaccine

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