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Acquired or non-acquired immunity after infection with the new coronavirus is one of the central questions in the current debate on the new coronavirus pandemic, even without many answers. A large study of people in New York who had Covid-19 brings what appears to be good news: Most infected people develop antibodies.
The study, funded by the National Institute of Allergy and Infectious Diseases (Niaid) and not yet reviewed by other researchers who were not involved in the research, looked at 1,343 patients with Covid-19 confirmed in tests or with self-reported symptoms of the disease. Virtually all had mild to moderate symptoms, and only 3% had to go to an emergency room.
Between March 26 and April 10, part of the people who participated in the study carried out PCR tests (the most accurate) and another part carried out antibody detection tests. Everyone who participated should already be asymptomatic.
Of the 1,343 patients, 624 had confirmation of Covid-19 by PCR. In this group, 511 had high levels of antibodies present (which also made them possible blood donors for patients still affected by the new coronavirus, a therapeutic option under study), 42 had weak levels and in 71 the antibodies were not detected.
Researchers at the Icahn Monte Sinai School of Medicine then reevaluated 64 of those with low antibodies or in whom no such defenses were found. They observed that 57 of them had increased antibodies between the two tests (an average time interval of 13 days). In total, in this subgroup, only four people remained with a weak presence of antibodies and three remained negative for the presence of protection.
Among the 719 patients not confirmed by the Covid-19 tests, 250 had high levels of antibodies, 19 had low levels, and 436 were negative for their presence, which the researchers said would indicate that these people were not truly infected. , that the antibody detection tests failed or that there was not enough time for an immune response. This group was evaluated, on average, 19 days after the end of the symptoms.
The scientists behind the research say the results do not support the claim that immunity exists after Sars-CoV-2 infection, but that because of what is known about other pathogens, people who have already become ill may believe some level of protection. against the virus
They also observed that it takes 7 to 50 days for the antibody response in the body to be detected after the onset of symptoms.
The scientists will monitor the antibody levels of the study participants for six months to see the duration of that immune response.
It was striking to the investigators that 19% of the research participants continued positive PCR tests even after claiming that the symptoms of Covid-19 had completely disappeared. This can influence the virus transmission window. However, detection can only point to the presence of non-infectious fragments of the virus in the person.
One of the limitations of the study was the fact that the patients have not so severe cases of Covid-19, which prevents conclusions about the most serious cases of the disease. Furthermore, there may be a bias in the selection of the participants, taking into account that the participants were recruited from the reports made by themselves.
The researchers also state that it is necessary to understand, in future studies, who are the patients who do not develop an immune response to the coronavirus and why.
