Scientists from Rockefeller University (New York), who published a study on the resource biorxiv.org, argue that they have found convincing evidence that those who have recovered from covid are able to defend themselves much faster and more effectively against infection when they encounter the virus again.
It is unclear how long the immune system provides protection, but researchers believe that it is likely to provide protection to those who get sick over the course of several years. This explains why confirmed re-infections are still extremely rare.
When a person becomes infected, the immune system defends itself and attacks the virus from several fronts at once. T cells detect and destroy infected cells, thus preventing the spread of the virus. B cells release antibodies into the blood, which neutralize the virus and prevent it from entering the cells. When a person recovers, the immune system stops defending itself, but it remembers the virus: this information is stored in memory T cells and memory B cells, which, as soon as the virus returns, are immediately called for help.
Many previous studies have shown that antibodies to coronavirus, formed as a result of the disease, weaken after a few months, which threatens the loss of immunity. However, the authors of the new work, after studying 87 patients and finding that antibodies do weaken (after six months, about a fifth of their maximum level remains), they believe that this is not so important. Because six months later, antibodies produced by memory B cells evolved and became more powerful.
After re-infection, they can be released much faster than with the initial infection - within a few days, and effectively fight the disease. Harmless residues of coronavirus, or protein fragments from inactive viral particles, can remain in the intestines of those who have been ill and help maintain the memory of the immune system.