medwireNews: It is possible for rituximab-treated patients with no response to two messenger (m)RNA vaccines against SARS-CoV-2 to respond to a third dose, with similar response rates among those switching to a vector vaccine and those given a third dose of the same vaccine, research suggests.
These findings are based on a randomized controlled trial involving 55 rituximab-treated patients with rheumatic or neurologic diseases – most commonly arthritis (38%) or connective tissue disease (29%) – who had no detectable antibodies against the SARS-CoV-2 spike protein at least 4 weeks after their second dose of the Pfizer–BioNTech (BNT162b2) or Moderna (mRNA-1273) vaccine. Participants were stratified by the presence or absence of peripheral B cells and randomly assigned to receive a third vaccination with the vector-based Oxford–AstraZeneca (ChAdOx1 nCoV-2019) vaccine, or to receive a third dose of their initial mRNA vaccine.
Daniel Aletaha (Medical University of Vienna, Austria) and colleagues report in the Annals of the Rheumatic Diseases that the proportion of participants with detectable anti-SARS-CoV-2 antibodies (ie, seroconversion) 4 weeks after receiving their third vaccine was not significantly different among those switching to the vector vaccine and those given a homologous third dose, at 22% and 32%, respectively.
The overall seroconversion rate across the two groups was 27%, with a median anti-SARS-CoV-2 antibody concentration of 15.7 binding antibody units/mL. Patients with detectable peripheral B cells prior to their third vaccination had higher seroconversion rates than those without, at 67% versus 8%, and the researchers say that having detectable B cells “was the strongest determinant for seroconversion” on exploratory post-hoc analysis, with an odds ratio of 22.7.
“These data support the critical consideration of the timing of rituximab treatment, potentially suggesting postponing its application until after vaccination, or that vaccination should be timed after peripheral B cells have repopulated,” write the researchers.
They also evaluated T-cell responses before and after the third vaccine dose in 36 patients with available matched samples. The proportion of individuals with detectable SARS-CoV-2-specific T cells improved from 75% to 100% in the vector vaccine group, and from 63% to 81% in the homologous mRNA vaccine group.
Furthermore, in the whole study population, having a third vaccine dose decreased the proportion of patients with neither a humoral nor a cell-mediated immune response from 31% to 6%, say Aletaha et al.
These findings support “an additional booster vaccination in non-seroconverted patients irrespective of a heterologous or homologous vaccination regimen,” they write.
The investigators note that no serious adverse events related to vaccination were observed in the study.
medwireNews is an independent medical news service provided by Springer Healthcare Ltd. © 2022 Springer Healthcare Ltd, part of the Springer Nature Group
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