Without symptoms, the immunity may be lower according to a study chinese
People who have been infected by the new coronavirus do not develop symptoms of the disease Covid-19, may have lower antibody levels against the virus than those who are more seriously ill, suggest chinese researchers today in the journal Nature Medicine.
The researchers warn, as a result, risks to set up “passports of immunity” which would be expected to ensure that their holders are protected against the disease.
The study describes the immunological and clinical, the cases of 37 people without symptoms whose infection has been diagnosed by a virologic test (RT-PCR nasopharyngeal swab) in the district of Wanzhou (in Chongqing municipality, southwest China) by the 10th of April 2020.
Among these 37 patients, asymptomatic – identified in a group of 178 people with the infection is due to the new coronavirus, SARS-CoV, 22 were women and 15 men, aged from 8 to 75 years (median age : 41 years).
The authors Have Long Hua of the medical University of Chongqing and his colleagues, have found that these patients put in isolation in hospital had a median duration of viral excretion of 19 days compared to 14 days in 37 patients with symptoms (fever, cough, shortness of breath…). The duration of excretion is not equivalent, however, an infectivity which remains to be assessed, are the responsibility of the authors.
Eight weeks after leaving the hospital, the levels of neutralizing antibodies, which confer a priori immunity against the virus, had decreased in 81.1% of patients without symptoms, compared to 62,2% in symptomatic patients.
To further elucidate the immune response, the researchers measured certain substances (cytokines and chemokines) in the blood and observed their low levels in asymptomatic patients, showing an inflammatory response reduced.
“In this study, we observed that the rate of IgG and neutralizing antibodies in a high proportion of people who have recovered from an infection with SARS-CoV-2 begin to decrease within 2 to 3 months after infection“they write.
These data, together with previous analyses of neutralizing antibodies, highlight the potential risks of use “passports of immunity“and plead in favour of public health interventions (social distancing, hygiene, isolation of high-risk groups, screening for generalized), according to the authors.
They advocate for further research “of any emergency“on larger groups of patients with and without symptoms to determine the duration of immunity from antibodies.
In spite of the small number of patients, “this corresponds to some of the concerns according to which the natural immunity to the coronavirus may be short-lived“according to the professor of immunology british Danny Altmann, who was not involved in this study.
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