February 14, 2022: Findings from a systematic review and meta-analysis confirmed the impact of rituximab and other anti-CD20 therapies on vaccine response. The authors reported "heterogeneous" responses, with particularly low seroconversion rates among people with recent B-cell depletion.
January 20, 2022: A randomized controlled trial involving rituximab-treated patients with rheumatic or neurologic diseases demonstrated that it is possible for those with no response to two mRNA vaccine doses to mount an antibody response to a third dose. There were no significant differences in antibody response rates among those switching to a vector vaccine and those given a third dose of the same vaccine.
In contrast to these findings, a study of patients with antineutrophil cytoplasmic antibody-associated vasculitis on various maintenance treatment regimens found that none of those given rituximab within the past year developed neutralizing antibodies against the SARS-CoV-2 B.1.617.2 (delta) variant.
January 10, 2022: Results from two studies indicate that among people treated with rituximab, those with a longer time since their last infusion may have an increased likelihood of mounting an antibody response to vaccination. The authors of one of the studies – Ingrid Jyssum (Diakonhjemmet Hospital, Oslo, Norway) and team – say that “[f]or an optimal response, the interval between rituximab infusion and vaccination should be as long as possible, preferably at least 9 months.”
In an additional study, researchers identified a minimum level of B cells in the peripheral circulation that may serve as a biomarker for response to COVID-19 vaccines among rituximab-treated patients.
November 30, 2021: Findings from a small study suggested that delaying the administration of booster doses until B-cell repopulation may warrant investigation as a strategy to improve vaccine response rates among rituximab-treated patients. The team found a significant correlation between B-cell count at the time of the third vaccine dose and neutralizing antibody concentrations 1 month later.
September 13, 2021: The RituxiVac study showed that people treated with B cell-depleting therapy have reduced humoral and cell-mediated immune responses to mRNA vaccines against COVID-19. Daniel Sidler and colleagues, from the University of Bern in Switzerland, also identified several predictors of humoral immune responses, including anti-CD20 therapy timing and peripheral CD4+ and CD19+ cell counts. While these findings require further validation, the researchers conclude in The Lancet Rheumatology that they "could provide guidance for coordinating both the administration of SARS-CoV-2 vaccines and B-cell depleting agents in this population.”
May 11, 2021: A small study from Daniel Aletaha (Medical University of Vienna, Austria) and team found that although rituximab-treated patients with depleted B cells have an impaired antibody response to the Pfizer–BioNTech (BNT162b2) vaccine, these people may still be able to mount a T cell-mediated response. They conclude that rituximab "may not have to preclude SARS-CoV-2 vaccination," but stress the need for more research into whether T cell-mediated immunity is sufficient to protect against COVID-19.