Does treatment timing impact COVID-19 vaccine response?
Given enough time, B-cell reconstitution will occur in patients taking rituximab. With that in mind, is it beneficial to wait a certain amount of time after a patient has stopped rituximab therapy or time since their last dose before giving them a COVID-19 vaccine? In their guidance on COVID-19 vaccines for patients with rheumatic and musculoskeletal diseases, the American College of Rheumatology said there is moderate evidence to consider “optimal timing of dosing and vaccination with the rheumatology provider before proceeding.”
“Guidelines and preliminary studies of serologic response to COVID vaccine in rituximab-treated patients have suggested that longer time from last rituximab exposure is associated with a greater likelihood of a serologic response,” Dr. Spiera said.
In a brief report published in Arthritis & Rheumatology, Dr. Spiera and colleagues performed a retrospective chart review of 56 patients with varying levels of last exposure to rituximab who received a COVID-19 vaccine. Their results showed that, when patients were vaccinated 6-12 months after the last rituximab dose, 55% were seronegative, and when this was more than 12 months, only 13% were seronegative, compared with seronegativity in 86% who were vaccinated less than 6 months after their last rituximab dose.
The RituxiVac trial, conducted by researchers in Switzerland, also examined vaccine responses of 96 rituximab-treated patients who received Comirnaty or Spikevax; results recently published in The Lancet Rheumatology showed findings similar to other studies, with reduced humoral and cell-mediated responses. In the RituxiVac trial, the median time to last anti-CD20 treatment was 1.07 years.
“The typical interval between rituximab doses [for treatment of rheumatoid arthritis, as well as for remission maintenance in antineutrophil cytoplasmic antibody–associated vasculitis] is typically 6 months, and this has become widely used as the interval from last rituximab to time of COVID vaccination, with a recommendation to wait 4 weeks (if possible) from time of vaccination until the next rituximab administration,” Dr. Spiera explained. However, this window seems to vary depending on the study.
Recent research published in Arthritis & Rheumatology indicates B-cell levels could be a relevant indicator for humoral and cell-mediated response in patients with rheumatic diseases treated with rituximab, with a level of 10 B cells/mcL (0.4% of lymphocytes) identified as one potential marker for likely seroconversion following COVID-19 vaccination.
“In some smaller case series, it has been further recognized that rituximab-treated patients who were beginning to reconstitute peripheral B cells were most likely to respond serologically. Our present study confirmed those findings, demonstrating that the presence of detectable B cells was strongly associated with vaccine responsiveness, and affords complementary information to time from last [rituximab dose] in informing the likelihood of a vaccine response,” Dr. Spiera said.
However, the literature is limited in this area, and an exact cutoff for B-cell counts in these patients isn’t currently known, Dr. Jyssum said. A better metric is time away from anti-CD20 therapies, with CD19 cell count being highly correlated with last infusion.
Dr. Spiera agreed that there is no consistent B-cell percentage that works as a cutoff. “In our study, we looked at it as a binary variable, although we did find that a higher percentage of B cells in the peripheral lymphocyte population was associated with a higher likelihood of seroconversion. We did not, however, identify a ‘threshold’ for vaccine serologic responsiveness.”