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Very low rate of humoral response after a third COVID-19 vaccine dose in patients with autoimmune diseases treated with rituximab and non-responders to two doses
  1. Samuel Bitoun1,
  2. Jérôme Avouac2,
  3. Julien Henry1,
  4. Roba Ghossan2,
  5. Omar Al Tabaa2,
  6. Rakiba Belkhir1,
  7. Gaetane Nocturne1,
  8. Alice Andrée Mariaggi3,
  9. Flore Rozenberg3,
  10. Christelle Vauloup-Fellous4,
  11. Xavier Mariette1 and
  12. Raphaèle Seror1
  1. 1Rheumatology, Université Paris-Saclay, Inserm UMR 1184, Hôpital Bicêtre, Assistance Publique-Hôpitaux de Paris, FHU CARE, Le Kremlin-Bicetre, France
  2. 2Rheumatology, Université Paris Cité Hôpital Cochin, AP-HP.CUP, Paris, France
  3. 3Virology Department, Université Paris Cité, Hôpital Cochin, AP-HP.CUP, Paris, France
  4. 4Division of Virology, Department of Biology Genetics and PUI, Paris Saclay University Hospital, APHP, INSERM U1193, Université Paris Saclay, Villejuif, France
  1. Correspondence to Dr Samuel Bitoun; samuelbitoun{at}

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Patients with autoimmune diseases (AIDs) treated with rituximab (RTX) are at increased risk of death from COVID-19 infection. They have a diminished humoral response despite a preserved T-cell response to two doses of mRNA COVID-19 vaccines.1 2 It is currently not established how efficient the third dose is in this population. The objective of this study was to assess the effect of a third dose of COVID-19 vaccine on the anti-spike (anti-S) response in patients with AID treated with RTX and non-responders to two doses.

This bicentric observational real-life study included patients with AID treated with RTX having no anti-S response after two doses between March and October 2021. Response was defined as anti-S of ≥49 binding antibody units (BAU)/mL, the threshold being associated with a detectable neutralising response.1 Anti-S response was measured using various ELISA kits, but all results were expressed in BAU/mL, which means that the technique has been calibrated with WHO standards. Some provided results with an upper quantification limit of 243; we thus applied this threshold for all. Responders and non-responders were compared to identify factors associated with response to the third dose. Some patients without response to a third dose had a fourth dose. Patients were not involved in the conduct of this study.

We included 62 patients with AID, previously treated with RTX, who had no response to two doses of COVID-19 vaccine. Only 9/62 (14,5%) patients responded to a third dose. Responders and non-responders after three doses had similar demographic characteristics (table 1). Detectable anti-S following two doses, but below the neutralising threshold (<49 BAU/mL), were significantly more frequent in responders (4/8 (50%)) than non-responders (2/48 (4%)) (p=0.0025) after the third dose. There was a positive correlation between anti-S levels after dose 3 and time between second and third doses (r=0.39, p=0.001; online supplemental figure 1). Likewise, the median time between the second and third doses was numerically, but not significantly, higher in responders than in non-responders (129 vs 84 days, p=0.30). There was a trend towards a correlation between the anti-S levels after the third dose and the time between the last RTX infusion and the third dose (r=0.23, p=0.07; online supplemental figure 2). There was a similar proportion of responders (28%) and non-responders (33%, p=0.71) that received an infusion of RTX between the second and third vaccine doses. Numerically, more non-responders received methotrexate comedication (62%) than responders (33%, p=0.15). Overall, seven patients (including five (71%) having undetectable and two (29%) having <49 BAU/mL anti-S titers after the third dose) received a fourth dose and 4 (57%) responded. The antinucleocapsid (N) status was available for all patients at baseline, and in 54/62 (87%) after third dose. All samples were negative for anti-N, except in one patient who was positive since baseline but did not have anti-S response to the third dose.

Table 1

Characteristics of patients without response after the second dose of vaccine treated with RTX for AIDs according to their seroconversion after the third dose

Few data exist on response to a third vaccine dose in RTX-treated patients having no response after two doses.3 4 We here observe a very low response rate to a third dose of COVID-19 vaccine (14.5%) compared with a 44% rate of response in solid organ transplant recipients after a third dose in patients without response to two doses5 or compared with a previously published report of 17 patients with rheumatoid arthritis where all but 2 patients responded.4 However, none of these patients received RTX. Also, compared with this previous report, our definition of non-response to two doses was more stringent according to our previous findings.1 Finally, our results are in line with the very low response rate observed with RTX in a small previous study.3 This reinforces our finding that having a detectable response, even low, to two doses predicts the response to the third dose. Also, we observed that longer intervals between the second and third doses might be associated with better response, as previously observed in patients on dialysis not treated with RTX.6

As a limitation, we did not assess circulating B cells at the time of vaccine injections, which might influence humoral response. However, time since the last RTX could be a proxy of B-cell repopulation. Also, we did not assess the T-cell response, which is, however, less impacted by RTX.1

In conclusion, a third dose of COVID-19 vaccine led to only 14,5% of response in RTX-treated AID patients non-responding to two doses. A detectable anti-S response after second dose, even below the neutralising threshold, might positively influence response to a third COVID-19 vaccine. This suggests that, in case of total absence of humoral response after the second dose, the expected response rate of a third dose is very low. Now, alternatives to vaccination such as prophylactic anti-S antibodies exist7 and could be useful approaches that should be evaluated in this context.

Ethics statements

Patient consent for publication

Ethics approval

This study involves human participants. The protocol and the informed consent document received institutional review board/independent ethics committee approval before initiation of the study (‘Comité de Protection des Personnes’ Paris Ile de France I, no. CPPIDF-DAP13) and CPP Sud Méditérrannée number 2020-A00509-30. The participants gave informed consent to participate in the study before taking part.


We warmly thank Sylvie Miconnet, Isabelle Bonnet, Elodie Rivière, Pauline Richebé, Stephan Pavy, Asmaa Mamoune and Marie-Armelle Roudault for their high implication in the vaccination process of the patients.


Supplementary materials

  • Supplementary Data

    This web only file has been produced by the BMJ Publishing Group from an electronic file supplied by the author(s) and has not been edited for content.


  • Contributors SB, JA, JH, RG, OAT, AAM, FR, RB, GN, CV-F, XM and RS acquired the data. SB, RS, XM and JA, performed the analysis. SB, JA, JH, RG, GN, CV-F, XM and RS wrote the paper. SB, JA, JH, RG, OAT, AAM, FR, RB, GN, CV-F, XM and RS reviewed and approved the final manuscript.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.