Blood samples donated before the pandemic helped them in this.
Initially, the researchers intended to study specific coronavirus antigens that provoke a strong immune response. This information is very important for creating a future vaccine.
However, at the same time, scientists decided to look at the reaction of T-lymphocytes from donated blood, which was donated in the period from 2015 to 2018. It turned out that almost half of the samples showed a specific T-cell response to COVID-19 antigens.
Immunologists have suggested that cross-reactive immunity is the secret. Apparently, these people had previously been ill with other coronaviruses, which provoke an ordinary SARS.
However, it is too early to draw concrete conclusions. Now, American researchers intend to more thoroughly study T cells in patients who have had other coronaviruses before they become infected with COVID-19, and then after their recovery.
Read the material: Doctors put forward a new version regarding re-infection with coronavirus