NIH Some vaccines offer long-lasting protection. For instance, the tetanus vaccine provides protection for at least 10 years. With other vaccines, protection may begin to decline within a few months. To provide enduring immunity, a vaccine must elicit production of long-lived plasma cells, a type of immune cell that matures over time in the bone marrow and can rapidly trigger production of disease-fighting antibodies.
The mRNA vaccines developed for the SARS-CoV-2 virus have proven effective at preventing severe COVID-19 and reducing hospitalizations. These vaccines trigger production of antibodies that home in on the virus’s spike protein. But protective antibodies can begin to fade as soon as three months later and lead to breakthrough infections. Researchers have been puzzled by this waning protection, since SARS-CoV-2-specific immune cells can often be found in the bone marrow.
To better understand why protection against SARS-CoV-2 dwindles months after vaccination, a research team led by Dr. F. Eun-Hyung Lee of Emory University took a closer look at immune cells in the bone marrow of 19 healthy adults. Participants ranged in age from 20 to 65. All had previously received between two and five doses of mRNA COVID-19 vaccines. Samples of their bone marrow were evaluated within 33 months after receiving their initial COVID-19 vaccine shot.