Scientists at King's College London studied the immune response in 90 ill patients and doctors and made a disappointing discovery: three months later, only 17% of the subjects had the same level of antibodies.
According to a study published as a preprint on the MedRxiv website, antibody levels decrease within three months after infection, which may make patients vulnerable to infection again.
The first antibody test showed a very high antibody level in 60% of patients, but after three months it remained in only 17% of patients.
“In some cases, the level of antibodies decreased by 23 times, in others it was completely depleted,” the researchers write.
The authors emphasize that their findings are very important for evaluating mass antibody testing, and most importantly, in predicting the duration of the immune response that the COVID-19 vaccine should provide.
“Further research is needed using sequential samples of these patients to fully determine the longevity of the immune response. Studies are also needed to determine the level of antibodies to protect against reinfection, ”the scientists emphasized.
Previously, researchers at the Karolinksa Institute in Sweden carried out an immunological analysis of 200 patients who were ill, including those who transferred COVID-19 in mild or asymptomatic form. Antibodies were not detected in 30% of the patients, but the so-called T-cell immunity was detected, and it was twice as high as in people with antibodies. T-cells (or T-lymphocytes) store information about previously acting antigens and contribute to the formation of immunity to transferred infectious diseases.
Researchers concluded that the level of collective immunity can be much higher, because worldwide scientists in their estimates rely solely on the number of patients with antibodies.
“Probably now we are underestimating the number of people who have some kind of immunity. Does this mean that such people are fully protected or in the future the disease will proceed in their milder form or asymptomatically, now it’s hard to say, ”the scientists write.