Studies have shown that immunocompromised individuals may have a reduced response to COVID-19 vaccines, which could impact the development of antibodies to the spike protein. However, there is evidence that administering an additional dose (i.e. a third dose) of the COVID-19 vaccine may increase the antibody response in immunocompromised individuals.
A study published in the New England Journal of Medicine in September 2021 found that after receiving a third dose of the Pfizer-BioNTech vaccine, 33% of solid-organ transplant recipients and 50% of patients receiving hemodialysis had a detectable antibody response to the spike protein, compared to 3% and 4%, respectively, after the second dose. Another study published in the same journal in November 2021 showed that after a third dose of the Moderna vaccine, 60% of solid-organ transplant recipients had detectable antibody responses to the spike protein, compared to 19% after the second dose.
These findings suggest that a third dose of the COVID-19 vaccine may be beneficial for immunocompromised individuals, although the level of protection offered by these antibodies and the duration of protection is still being studied. It's also important to note that the antibody response to the spike protein is not the only measure of vaccine efficacy, and that other immune responses, such as T-cell response, may also play a role in protection against COVID-19.
