It is noted that in May 2021, an enzyme-linked immunosorbent assay was performed on their blood samples on plates with immobilized RBD (coronavirus S-protein fragment).

In accordance with the survey data, the donors were divided into four groups: those who had been ill with COVID-19 and then vaccinated with Sputnik V;

not sick, vaccinated with "Sputnik V";

recovered from COVID-19, but not vaccinated;

not vaccinated and not sick (among which there may be asymptomatic recovered).

It is reported that "donors who underwent COVID-19 and then vaccinated with Sputnik V (group 1), the number of antibodies against coronavirus was the highest."

Anna Mikhailovna Timofeeva, Candidate of Biological Sciences, Junior Researcher of the Reparation Enzymes Laboratory of the Institute of Chemical Biology and Fundamental Medicine of the SB RAS, “this may be due to the fact that after a disease the human body is already familiar with viral proteins and the immune system gives a more powerful response. ".

According to data as of June 21, 17,378 cases of coronavirus infection were registered in Russia per day.

The total number of COVID-19 cases in the country has risen to 5,334,204. 

At the end of May, an immunologist, Doctor of Medical Sciences Vladislav Zhemchugov, in an interview with FAN, assessed the situation with COVID-19 in Russia.