At the onset of the COVID-19 pandemic, scientists were in a rush to develop a cure or defense against the growing disease, leading to the development of many effective vaccines. Like many other vaccines, the research on immunity continues to grow as new information continues to emerge. While the initial focus of the COVID-19 vaccine was primarily on neutralizing antibodies, evidence and sources indicate that T cells also play a crucial role in protecting individuals. 

Upon vaccination, the specific viral protein is introduced into the body, activating B cells to produce antibodies. These are considered the first line of defense because they can detect and neutralize the virus before infection (2). Though antibodies are important to fight against COVID-19, their effectiveness declines as the virus grows stronger with variants (2). In the case that the virus enters the host cell, CD8⁺ cytotoxic and CD4⁺ helper T cells are then activated. These cells work to eliminate the virus, thus preventing the spread of COVID-19 in the body and to others. Unlike antibodies, both B and T memory cells can hold onto crucial information to protect the body from future infections.

Researchers have investigated the importance of T cell immunity in patients who have recovered from COVID-19 by measuring T cell responses to peptides from the COVID-19 virus. Using the ELISPOT method, they were able to conclude that 52% of vaccinated patients showed positive T cell responses (3). Another study was also conducted in a nursing home, focused on elderly patients and their immune response to COVID-19 booster shots. When given the 3rd booster shot, the data indicated that their T cell responses increased from 74% to 97% with their CD8⁺ cytotoxic cells showing a significant boost (1). These findings demonstrate that T cells are a critical component in vaccine-immunity when up against severe diseases. 

While antibodies are a significant factor when fighting against COVID-19, the research on vaccine improvements should also prioritize T cell mechanisms. Not only do T cells attack the virus during infections, but they can also provide long-lasting protection, especially towards variants. With studies and data showing the significance of T cell response in vaccinated individuals, optimizing T cell immunity is essential to improving COVID-19 vaccines as well as other vaccines.

References

Carretero, D., Giménez, E., Albert, E., Colomer, E., Torres, I., Olea, B., Sánchez-Simarro, Á., & Navarro, D. (2024). SARS-CoV-2-Spike T-cell response after receiving one or two Wuhan-Hu-1-based mRNA COVID-19 vaccine booster doses in elderly nursing home residents. Journal of medical virology, 96(7), e29790. https://doi.org/10.1002/jmv.29790

E. John Wherry, Dan H. Barouch ,T cell immunity to COVID-19 vaccines.Science377,821-822(2022).DOI:10.1126/science.add2897

Krechetov, S. P., Vtorushina, V. V., Inviyaeva, E. V., Gorodnova, E. A., Kolesnik, S. V., Kudlay, D. A., Borovikov, P. I., Krechetova, L. V., Dolgushina, N. V., & Sukhikh, G. T. (2023). T-Cell Immunity in COVID-19-Recovered Individuals and Individuals Vaccinated with the Combined Vector Vaccine Gam-COVID-Vac. International journal of molecular sciences, 24(3), 1930. https://doi.org/10.3390/ijms24031930