In the event of an infection with the COVID-19–causing virus SARS-CoV-2, the immune system is activated, resulting in the production of antibodies and T cells that target viral proteins and remove the infection.
The recent Omicron variant of SARS-CoV-2 has unfortunately been shown to be able to evade antibody responses even in people who have been vaccinated against COVID-19; however,
new research published in Cell and led by investigators at the Massachusetts General
Hospital (MGH) indicates that T cell responses against the variant are still robust in most individuals who have had prior SARS-CoV-2 infection or vaccination, thereby providing protection against severe disease.
A total of 76 persons with and without prior SARS-CoV-2 infection in Chelsea, Massachusetts, were recruited for the study. The participants included both vaccinated and unvaccinated adults.
The researchers discovered that T cell responses against the Omicron spike protein were generally retained in persons who had previously been infected or vaccinated, as well as in individuals who had previously been infected and vaccinated and who had received a booster vaccination.
Individuals who had previously been infected with the virus developed reactions against other proteins in the virus as well.
“Even when antibodies failed to recognize Omicron, we discovered that T cells from the majority of individuals retained their recognition of the protein. This is encouraging news “Anusha Nathan, a medical student at the Ragon Institute of the Massachusetts General Hospital, MIT, and Harvard, is a co-lead author on the study.
Approximately 20% of people had considerably diminished T cell responses despite having previously been infected or vaccinated, and certain genetic features were found to be associated with this poor response. Fortunately, booster immunization appears to significantly increase T cell responses by a factor of twenty.
Gaurav D. Gaiha, MD, DPhil, a gastroenterologist at Massachusetts General Hospital and principal investigator at the Ragon Institute, says, “Our findings should provide some reassurance to the general public that the vast majority of previously infected and vaccinated individuals should have a T cell response to Omicron that provides protection against severe COVID-19.”
Although our research does not directly contradict antibody studies, it provides more encouragement for people to have booster immunizations to help defend against Omicron by significantly strengthening their T cell immunity.
The scientists speculated that their discovery that some people have lesser responses to Omicron may imply that the virus has evolved to be able to evade even T cell defense mechanisms.
So, says co-lead author Vivek Naranbhai, MBChB, Ph.D., DPhil, a hematology/oncology fellow at Massachusetts General Hospital and Dana-Farber Cancer Institute, “we must continue to work on vaccines that may be resistant to future variants and take sensible precautions like staying up to date on vaccinations, wearing masks, and testing appropriately to protect ourselves and our communities.”