A team of South African researchers, led by Catherine Riou and Wendy Burger, found that prior COVID-19-virus variant infections and vaccinations significantly increase T-cell immune response against the omicron virus. Our bodies have a second line of defense against infection: antibodies that are induced from infections with earlier COVID-19 virus variants or vaccines that were aimed at these variants. The omicron variation often avoids the first line of defense. Fast-reacting antibody can eliminate infections, but the amount of antibodies created in response to vaccines and other infections will decrease over time. That’s where our bodies’ second line of immunological defense—called T cells—comes into play.
Infected cells and vaccinations create T cells that lurk within our bodies, waiting for activation by disease microbes. Certain T cells attack infected cells and destroy them; others help the B cells produce additional antibodies that will protect against infection.
South African researchers sought to determine how the T cells of patients infected or vaccinated against earlier COVID-19 variations would respond to the omicron variation. The researchers were worried that the highly-mutated variant of the omicron would not be recognised by T cells that had received vaccinations or infected with earlier COVID-19 varieties. They report this to be false.
According to them, “Despite Omicron’s extensive neutralization escape, 70%-80% of T cells remain active.” It is possible for waning antibodies not to be sufficient to stop infection by the Omicron variant in significant numbers of individuals who were vaccinated. Nevertheless, T-cells remain 70-80 percent effective at defending against omicron infections.
Accordingly, researchers came to the following conclusion:
Omicron mutations do not have much effect on T cell responses, so vaccination or previous infection could still be a significant source of protection against serious disease. South Africa reported lower rates of severe and hospitalizations than the Delta wave. These milder Omicron outcomes may be due to cross-reactive T cells that have been activated by infection or vaccination. In the case of more mutations in the future, the strength and resilience shown here by the T cell responses bodes well.
This research shows that the Omicron variant is more likely to infect our body’s first line of defense. However, an additional line, either through vaccination or previous infection, will be able to stop it from happening with minimal harm. In a Twitter thread, virologist Burger further notes, “We still need to see how long T cell immunity lasts, but after SARS1 it was still detectable after 17yrs.”