Booster augments COVID-19 vaccine response in patients on rituximab despite prior failures
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A booster dose of both vector and mRNA vaccine products yielded improved immune response in immunosuppressed patients using rituximab who had previously failed to show a response to the first two vaccines, according to data presented here.
“We have learned from very recent data that patients under rituximab [Rituxan, Genentech] treatment have a severe [COVID-19] disease course compared with patients on other disease-modifying anti-rheumatic drugs,” Michael Bonelli, MD, of the Medical University of Vienna, said in his presentation at ACR Convergence 2021.
He noted that these patients have experienced higher rates of hospitalization, longer duration of hospitalization, persistent viremia and higher mortality compared with patients treated with drugs like TNF inhibitors. “One of the questions we actually raised was whether this might be due to insufficient vaccination response,” Bonelli said.
The group conducted a blinded, randomized clinical trial to determine the efficacy and safety of an additional booster vaccination with a vector versus an mRNA vaccine in immunosuppressed individuals who had not seroconverted after a two-dose schedule.
The analysis included 74 patients who had been treated with rituximab and failed to mount an antibody response to either the Pfizer or Moderna vaccines. They were randomly assigned either a third dose of the same mRNA vaccine or the Oxford-AstraZeneca vector vaccine.
The researchers stratified the cohort according to whether they did or did not have peripheral B cells.
The difference in SARS-CoV-2 antibody seroconversion rate between the two types of vaccines after 4 weeks served as the primary efficacy endpoint. Overall seroconversion, cellular immune response and safety parameters also underwent analysis.
The final analysis included 27 patients who received a vector-based vaccine and 28 who received an mRNA product.
Results showed that the overall seroconversion rate was 27%. “In this case, the primary endpoint was not reached,” Bonelli said.
However, response rates were 22% for the vector products and 32% for the mRNA vaccines. “Humoral immune response was dependent on the presence or absence of peripheral B cells,” Bonelli said.
In terms of cellular immune response after a booster dose, there was an increase from 75% to 100% response rate for the vector vaccines and from 63% to 81% for mRNA products.
Safety data showed no severe adverse events related to vaccination.
“Antibody production is actually possible in non-seroconverted immunosuppressed patients who basically failed to respond to primary vaccination,” Bonelli concluded. “We therefore recommend an additional vaccination for all immunosuppressed patients.”
In addition, Bonelli urged clinicians to consider the timing of rituximab doses as part of a patient’s COVID-19 vaccine schedule.
Perspective
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Jeff R. Peterson, MD
In this study, Bonelli and colleagues seek to answer an important question for rheumatologists worldwide: Should our patients be receiving a COVID-19 booster if they are immunocompromised and did not receive an adequate response from the first two vaccinations?
Seroconversion rates were followed in patients who had failed to seroconvert after the first two COVID-19 vaccinations with either Pfizer or Moderna products. Seroconversion rates were 22% for the AstraZeneca vector vaccine and 32% for a repeat mRNA vaccine but, more importantly, specific T-cell responses were observed in 100% of the vector and 81% of mRNA-vaccinated patients with newly induced humoral response occurring in 82% of patients.
Although the sample size was quite small, this data suggests that a third vaccine, regardless of the type, is helpful for patients who have not seroconverted and is a good step forward in our attempts to protect our immunocompromised patients from COVID-19 infection. I, for one, will be recommending a booster shot for all of my immunocompromised patients.
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Bonelli M. Abstract L17. Presented at: ACR Convergence 2021; November 5-9, 2021 (virtual meeting).
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