Scientists from the USA and Canada investigated how long the immunity lasts in those who have undergone a coronavirus infection. It turned out that antibodies to COVID-19 persist in the body for at least three months after a person has been ill with pronounced symptoms.
The results of relevant studies are published in the journal Science Immunology.
According to them, in response to the COVID-19 virus, the human immune system produces proteins called antibodies. Depending on how long long-acting IgG antibodies remain in the blood of a patient who has been ill, its protection from re-infection depends.
Most patients who had symptoms for at least two weeks had elevated IgG levels after four months. This means that they have retained protective antibodies. Only three people completely lost their IgG antibodies during this time.
For the first time, scientists have discovered antibodies not only in blood, but also in saliva. This is a very interesting finding, the researchers say, as it allows saliva to be used as an alternative biofluid for antibody testing. This is especially true for identifying those who are primarily infected - a standard PCR test - a nasal swab - is effective only in the first few days after infection, and then it loses its sensitivity. For patients whose symptoms persist for at least eight days, according to the authors, it can be supplemented with a saliva antibody test.
The results of two studies conducted independently of each other coincide and allow us to say that people who have had coronavirus with obvious symptoms, immunity persists for at least three months.