New data support the assumption that those who have been vaccinated and those who have recovered who become infected with Omikron are less likely to become seriously ill. As the preprint describes, certain immune cells in vaccinated and convalescent patients react similarly to Omikron as to older variants. You can therefore fight the new variant even though its spike protein has mutated so strongly that antibodies created by the vaccinations or an infection with an earlier variant hardly protect against infection. The so-called T cells are usually preserved longer than antibodies after an illness or vaccination and play a key role in protecting against a severe course.
The group headed by Catherine Riou and Wendy Burgers from the University of Cape Town looked for evidence of two types of T cells in blood samples from 70 vaccinated and convalescent people: those with the CD8 receptor, which destroy the infected cells, and those with the CD4 receptor, which cause Stimulate the formation of antibodies. To do this, the researchers brought cell cultures from people who were vaccinated or recovered around a month and a half ago into contact with the characteristic antigens (surface proteins) of various virus variants.
In 70 to 80 percent of the cases, the hoped-for T-cell response could be observed on Omikron – similar to the older variants Beta and Delta. Up to a month after the vaccination, the response could be observed in 85 percent of the cases. The group concluded that Omikron recognized the specific T cells of the vaccinated and convalescents almost as well as the original Wuhan variant. And this T-cell immunity helps protect against severe Covid-19.
The role of T cells in immune defense
T cells, together with B cells and the antibodies they generate, form the acquired immune response. The T cells are white blood cells that recognize foreign structures such as pathogens by certain characteristics, the antigens. Like a patrol watch, they search the body for the cell changes for which they have been trained. There are guards who kill an infected cell themselves: the T killer cells with so-called CD8 receptors (T cells with the CD8 molecule on the surface). The T helper cells with CD4 receptors do not intervene by themselves, but get help: They use messenger substances to stimulate the B cells to form tailor-made antibodies. These bind to the antigens of the virus and thus initiate its end.