ABSTRACT
In patients with common variable immune deficiencies, primary vaccination followed by two booster doses is recommended for protection against COVID-19. Seroconversion has been shown in 60% of patients. We have no information on whether serum antibodies reflect the generation of durable immune memory. In a longitudinal study on 47 common variable immune deficiencies patients who received the third and fourth vaccine dose, we show that the measurement of specific antibodies is not sufficient to predict the establishment of immune memory and the ability to respond to antigen re-exposure. Our results indicate that the combination of antibodies and memory B cells responses represents a more reliable read-out of vaccine immune efficacy in vulnerable patients. This analysis may not only identify individuals remaining unprotected after vaccination and unable to respond to additional booster doses, but also address the search for the underlying immune defect and suggest patient-tailored management strategies.