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Humoral and cellular immune responses after standard two-dose COVID-19 vaccination are reduced in immunosuppressed patients with antineutrophil cytoplasmic antibodies associated vasculitis (AAV).1–3 Emerging variants such as B.1.617.2 (delta) are of particular concern because of their higher transmissibility and partial immune escape.4 AAV patients with lower neutralising antibody levels may become particularly susceptible to these variants of concern and additional booster vaccination may be required.
We performed a prospective observational study at three different German vasculitis centres to investigate humoral responses against the variant of concern B.1.617.2 after a third vaccine dose with BNT162b2 in 21 patients with AAV on immunosuppressive maintenance therapy. All individuals met the 2017 provisional American College of Rheumatology (ACR)/European League Against Rheumatism (EULAR) criteria for AAV. We investigated antispike S1 IgG and surrogate neutralising antibodies a median (IQR) of 23 (21–58) days after standard two-dose COVID-19 vaccination, immediately before a third vaccine dose, as well as a median (IQR) of 21 (21–21) days after third vaccination (online supplemental material). The third vaccine dose was administered a median (IQR) of 103 (72–126) days after second vaccination. In addition, neutralisation activity against B.1.617.2 was analysed in vitro in SARS-CoV-2-infected VeroE6 cells after second vaccination and before and after the third vaccine dose (online supplemental methods).5 Patients were also stratified according to whether or not they had received rituximab treatment as maintenance therapy in the last year. Baseline characteristics and individual immunosuppressive regimens are given in (online supplemental tables S1 and S2).
After second COVID-19 vaccine dose, the median (IQR) anti-S1 IgG index was 1.6 (0.1–3.0) and the median (IQR) per cent inhibition of surrogate neutralising antibodies 34 (31–70; figure 1A). A median (IQR) of 103 (72–126) days after the second vaccine dose, both anti-S1 IgG and neutralising surrogate antibodies decreased to 0.1 (0.1–1.8) and 9 (0–35), respectively, and a third vaccine dose with BNT162b2 was subsequently administered (figure 1A). Anti-S1 IgG and surrogate neutralising antibodies significantly increased to a median (IQR) index of 5.6 (0.5–150) and a median (IQR) per cent inhibition of 56 (4–94) 3 weeks after the third vaccine dose (for both p<0.01; figure 1A). Most importantly, after second vaccination, only 6/16 (38%) patients showed neutralising activity against B.1.617.2 and this number decreased to 3/16 (13%) directly before third vaccination (figure 1B). Even patients with detectable antibodies in commercially available anti-S1 IgG or surrogate neutralising assays had no neutralisation against B.1.617.2. The number of patients with neutralising antibody activity against B.1.617.2 significantly increased to 12/21 (57%) 3 weeks after the third vaccine dose with a median (IQR) ID50 of 40 (0–160) compared with 0 (0–20) after second vaccination and to 0 (0–0) before third vaccination (p<0.05 and p<0.001; figure 1B). Individual courses of anti-S1 IgG, surrogate neutralising and B.1.617.2 neutralising antibodies before and after third vaccination are shown in detail in online supplemental table S3.
Patients receiving rituximab maintenance therapy had significantly lower anti-S1 IgG, surrogate neutralising and B.1.617.2 neutralising antibody levels after third vaccination compared with patients not receiving rituximab treatment (online supplemental table S3; figure 1C). Of note, 12/13 (92%) patients without rituximab treatment showed neutralising activity against B.1.617.2, whereas none of those treated with rituximab showed neutralising activity after a third vaccine dose (figure 1C).
Both anti-S1 IgG index and neutralising surrogate antibody activity correlated well with the ID50 value of neutralising B.1.617.2 activity of patients with AAV (figure 1D). However, exceeding the cut-off value for detection in both commercially available assays did not necessarily imply neutralising activity against B.1.617.2 at the same time.
Local adverse events occurred significantly more often after third vaccine dose compared with the first or second vaccination (for both p<0.001; online supplemental figure S1). However, systemic adverse events occurred infrequently after all vaccine doses and no patient experienced a disease flare during follow-up (online supplemental figures S1 and S2).
Consistent with other studies on the immunogenicity of COVID-19 mRNA vaccines in immunosuppressed patients with autoimmune diseases, our data indicate that most individuals have detectable antibody levels in commercially available assays after standard two-dose vaccination, but at significantly lower levels as compared with healthy individuals.1 6 7 Notably, patients treated with rituximab had particularly low seroconversion rates6 7 without detectable neutralising antibody activity against B.1.617.2 in our study. In a first case series on a third vaccine dose in three patients with AAV treated with rituximab, the booster dose was only associated with detectable humoral response in one patient.8 In our study, no patient treated with rituximab in the last year showed neutralising activity against B.1.617.2 after a third vaccine dose. However, in patients with AAV not treated with rituximab, a third mRNA vaccine dose resulted in significantly higher B.1.617.2 neutralisation compared with standard two-dose mRNA vaccination.
Summarised, this study suggests that immunosuppressed patients with AAV may not be adequately protected against B.1.617.2 after standard two-dose COVID-19 vaccination. A third vaccine dose with BNT162b2 induced a strong neutralising antibody activity against B.1.617.2 in most individuals; however, patients receiving rituximab maintenance therapy showed no humoral vaccine response even after a third vaccine dose.
Patient consent for publication
This study involves human participants and was approved by Ethics Committee of Uniklinik Heidelberg: S-416/2021 Participants gave informed consent to participate in the study before taking part.
The authors thank Iris Arnold and Sabine Bönisch from the Department of Nephrology, Heidelberg University Hospital, Verena Backendorf from the Department of Immunology, Heidelberg University Hospital and Heeyoung Kim from the Department of Infectious Diseases, Molecular Virology, Heidelberg University Hospital for their technical support.
Handling editor Josef S Smolen
Contributors Contributed to the manuscript by planning the study: CS, LB, KK and MS, performed the experiments and collected the data: CS, MT, LB, MB, CN, FK, PR and PS, analysis and interpretation of data: CS, MT, LB, PS, CM and MS and preparation and revision of the manuscript: CS, MT, LB, PR, MZ, CM, WHS, RBergner, RBartenschlager and MS. All authors contributed to the article and approved the submitted version.
Funding Funding for this study has been received from Dietmar Hopp Stiftung. CS was funded by the Physician Scientist Program of the Heidelberg Faculty of Medicine. LB was funded by the Rahel Goitein-Strauss Program of the Heidelberg Faculty of Medicine. RBartenschlager was supported by the program for surveillance and control of SARS-CoV-2 mutations of the State of Baden-Württemberg, the German Federal Research Network Applied Surveillance and Testing (BFAST) within the Network University Medicine, the DKFZ@fightCOVID initiative and the Helmholtz Association’s Initiative and Networking Fund Project ‘Virological and immunological determinants of COVID-19 pathogenesis—lessons to get prepared for future pandemics (KA1-Co-02 ‘COVIPA’)’.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
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