Should people on immunotherapy get COVID vaccine?

Dear Dr. Roach: I am currently on rituximab immunotherapy. I have had my first Moderna vaccine, and my second shot is scheduled in four weeks. My oncologist is not sure how the rituximab affects the immunization and the effectiveness of the vaccine. Can you explain how people on immunotherapy should most effectively take the vaccine while undergoing treatment? My next immunotherapy is three days after my second Moderna shot. — P.H.

Dear P.H.: Rituximab is a monoclonal antibody directed against B cells, the cells responsible for making antibodies. It is used for cancer treatment of B cell-related malignancies, such as non-Hodgkin’s lymphomas and some leukemias. It is also used for autoimmune disorders such as rheumatoid arthritis and autoimmune skin diseases.

Because rituximab directly targets B cells, it is known to reduce effectiveness of vaccines, particularly polysaccharide vaccines such as Pneumovax, but it also blunts the response to the flu shot. When possible, it’s recommended to give vaccines either before starting rituximab or at least six months after completing rituximab treatment.

Your oncologist doesn’t know the effect of rituximab on the new COVID-19 vaccines because nobody does: They haven’t been studied at all. While it is very likely that the vaccine is safe, it is probable that the vaccine will not be as effective in a person taking rituximab. I would speculate that it would be reasonable to consider revaccination six months after completing rituximab. Perhaps by then we will have additional knowledge to guide treatment.