The slower antibody response in myelofibrosis patients after two doses of mRNA SARS-CoV-2 vaccine calls for a third dose

Fiorino, F.; Sicuranza, A.; Ciabattini, A.; Santoni, A.; Pastore, G.; Simoncelli, M.; Polvere, J.; Galimberti, S.; Auddino, S.; Barate', C.; Montagnani, F.; Sammartano, V.; Bocchia, M.; Medaglini, D.

Immunization with mRNA SARS-CoV-2 vaccines has been highly recommended and prioritized in fragile categories with higher risk of mortality after COVID-19 disease compared to healthy people, including patients with myelofibrosis (MF). Available data on the vaccine immune re-sponse developed by MF patients, and the impact of the treatment with the inhibitor of JAK-STAT signaling ruxolitimib, are still fragmented to support an informed decision for a third dose for this category of subjects. Here, we show that 76% of MF patients develop spike-specific IgG after the second vaccine dose, but the response has a slower kinetic compared to healthy subjects, suggesting a reduced capability of their immune system to promptly react to vaccina-tion. A reduced ACE2/RBD inhibition binding activity of spike-specific antibodies was also ob-served, especially in ruxolitimib treated patients. Our results contribute to answer the open question on the induction of the antibody responses in MF patients following vaccination with COVID-19 mRNA vaccines, showing a slow kinetic that support the need for a third dose of SARS-CoV-2 mRNA vaccines.