Even after mild infections with the SARS-CoV-2 Coronavirus, the human body would be producing a “robust” immune response, especially in the cells responsible for “remembering” the Virus. This is shown by a group of three different preliminary studies, which were published last week. Although they are still under review by other scientists, the findings point in the same direction: long-lasting immunity.
The first of these preliminary studies – led by the Swedish Center for Infectious Diseases – was published on August 14th and shows a “robust” immune response in patients with mild Coronavirus infections.
The immune response does not refer only to the antibodies, but also to the cells in charge of “remembering” the Virus. These are known as T cells and they are precisely the ones that showed a high presence.
The research analyzed the convalescent blood of 206 patients recovered from COVID-19, who had the disease of different intensities and contracted it between February and March. “Our data set shows that SARS-CoV-2 elicits a robust, broad, and highly functional memory T-cell response,” the publication notes. Because of this, people are unlikely to get reinfected and have a severe condition, they say.
Long-term studies are still lacking, but “this is exactly what one would expect to see. All the pieces are there for a fully protective immune response,” lead author Marion Pepper declared.
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Different but in the same direction
Another preliminary study from the University of Washington in the United States had similar findings, although it was conducted separately: recovered COVID-19 patients would have an extensive T-cell response. The preliminary results of this investigation were published on August 15th. However, they are also under review by the scientific journal Nature. According to these results, patients recovered from mild COVID-19 not only maintained their T-cell levels after three months, but they increased it in number.
“Memory lymphocytes specific for SARS-CoV-2 exhibited characteristics associated with potent antiviral immunity. (…) Individuals who recovered from mild COVID-19 symptoms had an expanded arsenal of immune mediators against SARS-CoV-2,” the publication notes.
A third study, from the University of Arizona, found data pointing in the same direction: “We conclude that immunity is durable for at least several months after SARS-CoV-2 infection.” This research analyzed the antibodies of 5,882 COVID-19 patients and noted that the “conclusions about the rapid loss of immunity to SARS-CoV-2 are premature and inconsistent with the data we present here.”
Immunity: the big question
Long-term immunity to COVID-19 is one of the big questions yet to be answered about the disease. This is because not enough time has passed to know if it is maintained after a year, for example.
A scientific study from the English University King’s College yielded results on the subject: 60% of the patients analyzed had a powerful antibody response after being infected with COVID-19. However, only 16.7% maintained high levels of antibodies three months later. But this is not the whole story, as the behavior of T lymphocytes is much less understood. These “memory cells” help the body to identify harmful agents.
While studies point to an abundant T-cell response, long-term research confirming long-lasting immunity is still lacking. According to the US Center for Disease Control (CDC), there are no documented cases of reinfection in recovered patients.
The uncertainty on this issue would impact, for example, the use of vaccines against COVID-19. Pharmaceutical companies, however, admit to continuing this line of study without knowing how long the immunity would last.