When an individual is infected with the COVID-19–causing virus SARS-CoV-2, the immune system is called into action to produce antibodies and T cells that target viral proteins and clear the infection.
It has become clear that the recent Omicron variant of SARS-CoV-2 can, unfortunately, escape antibody responses even in many people who have been vaccinated against COVID-19.
But in a new study from Massachusetts General Hospital, researchers found that T cell responses are still robust against the omicron variant in most people with COVID infection or vaccination, thereby providing protection against severe disease.
In the study, the team tested blood samples from 76 vaccinated and unvaccinated adults with and without prior SARS-CoV-2 infection.
They found that T cell responses in individuals with prior infection, vaccination, both prior infection and vaccination, and booster vaccination were largely preserved against the Omicron spike protein.
People with prior infection also had responses against other proteins in the virus.
The team showed that T cells from most individuals retained their recognition of Omicron even when antibodies did not.
Approximately 20% of individuals had significantly reduced T cell responses despite prior infection or vaccination, however, and certain genetic characteristics were linked with this poor response.
Fortunately, booster vaccination appeared to enhance T cell responses by twentyfold.
The team says the findings should provide some reassurance to the general population that the vast majority of prior infected and vaccinated individuals should have a T cell response to Omicron that gives protection against severe COVID-19.
The study also provides further impetus for people to get booster vaccines to help protect against Omicron by substantially increasing their T cell immunity.
The scientists noted that their discovery that some people have lower responses to Omicron may indicate that the virus can evolve to escape even T cells.
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The study is published in Cell and was conducted by Anusha Nathan et al.
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