Getting COVID-19 Could Weaken Your Immune System
E ven relatively easy bouts with COVID-19 can still take a toll on the immune system, according to a paper published Mar. 15 in the journal Immunity—particularly on T-cells, which provide long term and durable protection against viruses.
Mark Davis, a professor of immunology at Stanford University and director of the Stanford Institute for Immunity, Transplantation, and Infection, and his team made the discovery when studying T cell responses to SARS-CoV-2 among 72 people through the early months of 2021, as the first COVID-19 vaccines were becoming available. They used the most sensitive method available to track changes in T cell responses, relying on an engineered molecule that can detect up to five-fold more T cells targeting SARS-CoV-2 than other molecules. The researchers focused on three groups of people: those who were not yet vaccinated and had gotten COVID-19, those who were fully vaccinated with two doses of the Pfizer-BioNTech mRNA vaccine and had not been infected, and people who had gotten vaccinated after recovering from COVID-19.
The researchers looked at a group of T cells called CD8 cells, or killer T cells, which destroy and remove infected cells during the latter part of an infection. Davis was surprised to find that levels of CD8 cells were lower among people who had gotten vaccinated after recovering from COVID-19, compared to those who had been vaccinated and never infected. The results differ from changes in antibodies, which are the body’s first line of defense and help block viruses from infecting cells. Studies of COVID-19 patients show that antibody levels in people who have been vaccinated and infected tend to be slightly higher than levels of antibodies among those who have been vaccinated and never been infected—creating hybrid immunity. The opposite was true with CD8 cells. “Sometimes you do experiments and don’t always know what you’re going to get, and something jumps out at you, and that was the case here,” Davis says. The fact that they saw “dramatically lower CD8 or killer T cell responses than everyone else” indicated that “there was some damage—something was happening after the infection in these people.”
