A modest-sized study, but published in the scientific journal Nature recently, it raises some concerns about the length of protection that cures from Covid-19 would develop. According to the research, conducted in China by a team from the Chongqing Medical University (a branch of the Chinese Center for Disease Control and Prevention), antibody levels in cured patients decline rapidly: in 3 months of over 70%.
Sharp drop after 3 months
For the analysis, 37 symptomatic and 37 asymptomatic patients were examined: over 90% of subjects showed a sharp drop in IgG antibodies in 2-3 months, those that show that our body came in contact with the infection and that theoretically they protect us from filming Covid-19. The median percentage reduction was over 70% for both symptomatic and asymptomatic patients. In addition, 40.0% of asymptomatic individuals (and 12.9% of symptomatic individuals) it has also become seronegative for IgGin practice he no longer had them.
Antibodies and serological tests
Let’s talk about the antibodies related to the virus that are also being searched for in Italy today serological tests: are the IgM (Immunoglobulins M), which occur within 7 days from the appearance of the symptoms and allow to confirm the diagnosis of infection, and the IgG (Immunoglobulins G), produced after about 14 days, which are our “Immune memory”, they tell us that in the past we have come into contact with the virus and protect us from it although, in the case of Sars-CoV-2, we do not know how long and to what extent. This is why the Chinese study is an alarm bell and brings out the risks associated with the use of “immunity passports”.
What do we know so far
For now we know with some certainty that most people with Covid-19 develop antibodies within 19 days. It also appears that these antibodies are neutralizing, that is, capable of rejecting future virus attacks. Yet we don’t know how long immunity lasts that they grant. If we were to stand by this study we would say “months”. The hope is that SARS-CoV-2, on the other hand, will behave like the coronavirus counterparts SARS and MERS which respectively produce protective antibodies for 2 years and 34 months. The further problem associated with this specific virus is that the vast majority of people either he has no symptoms or falls ill blando: in this case we do not know if the induced immune response, of which the presence of antibodies is a spy, is truly protective or if these people risk a new infection. To have more certainties on the duration of protection, all that remains is to continue epidemiological studies repeat serological tests for the detection of fixed-term antibodies, for example every three months for those who tested positive for IgG.
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