Rituximab blocks protective serologic response to influenza A (H1N1) 2009 vaccination in lymphoma patients during or within 6 months after treatment

The monoclonal anti–CD20-antibody rituximab has become standard of therapy in CD20-positive B-cell lymphomas as a single agent or in combination with chemotherapy.^1,2  It is also used in autoimmune disorders, such as rheumatoid arthritis.³  Rituximab treatment results in rapid and prolonged depletion of normal B cells,⁴  and long-term therapy may lead to hypogammaglobulinemia.⁵  Cancer patients are often advised to receive seasonal influenza vaccinations.⁶  It has been shown that lymphoma patients treated with conventional chemotherapy alone may respond adequately to influenza vaccinations.^7-10  Rituximab may dramatically impair the humoral response to vaccination in rheumatoid arthritis patients,¹¹  but only a few studies have addressed this effect in rituximab-treated lymphoma patients.^12-14  We have conducted a controlled study where serologic response to the influenza A (H1N1) virus vaccine Pandemrix during the 2009 “swine flu” pandemic was analyzed in 67 lymphoma patients treated with rituximab monotherapy or in combination with chemotherapy within the last 6 months before vaccination and compared it with the response in 51 healthy controls.

Patients included in this study were either undergoing treatment with rituximab as a single agent or in combination with chemotherapy or had received such therapies within the last 6 months before vaccination. Controls were healthy volunteers taking the vaccine. Blood samples were drawn before (pretest) and at least 3 weeks after (posttest) vaccination. Thirty patients had samples taken before and after vaccination, in 37 patients only posttest samples were obtained. All controls had both pretest and posttest samples taken. Patients and controls received 1 dose of a monovalent adjuvanted influenza A (H1N1) virus vaccine (Pandemrix; Glaxo SmithKline). Antibody titers were determined using the hemagglutination-inhibition test with turkey red blood cells as indicator cells and influenza A/California/07/2009 (H1N1v) virus as test antigen¹⁵  starting at serum dilution 1:20. Results are given as the reciprocal value of the highest inhibitory dilution from the hemagglutination-inhibition test. An antibody titer ≥ 40 was considered protective. In addition, in the patient group, we measured CD3⁺, CD4⁺, CD8⁺, and CD19⁺ cell numbers and immunoglobulin levels before vaccination. The postsample values in patients and controls were compared using the Mann-Whitney U test or Wilcoxon test as appropriate (SPSS). The study was approved by the Regional Committee for Medical Research Ethics (REK 2009/6195). All participants gave written informed consent in accordance with the Declaration of Helsinki.

A total of 71 lymphoma patients and 85 controls were recruited to the study. Four patients and 34 controls who had a prevaccination titer of > 40, indicating previous exposure to the H1N1 influenza virus, were excluded, leaving 67 patients and 51 controls (38 females and 13 males) for the final analysis. The median age of patients was 63 years (range, 24-82 years) and for controls 47 years (range, 24-68 years). The clinical description of patients is given in Table 1. The majority of patients were non-Hodgkin B-cell lymphoma of different subtypes. Most patients had received combination treatments, only 7 had been treated with rituximab as a single agent. Among lymphoma patients, only 5 persons had a measurable but nonprotective antibody titer of 20 after vaccination. The remaining 62 patients had no detectable titers at all. By contrast, 42 of the 51 controls (82.4%) had a postvaccination antibody titer ≥ 40, 8 had a titer of 20, and only 1 showed no response (Figure 1). This gives a sero-protection rate of 0% and 82% in patients and controls, respectively. The median value of immunoglobulins CD3⁺, CD4⁺, and CD8⁺ cells counts were within normal ranges among patients. CD19⁺ B cells were undetectable in the majority of patients (data not shown).

We demonstrate that lymphoma patients treated with rituximab as a single agent or in combination with chemotherapy fail to mount a protective antibody response after influenza A(H1N1) 2009 vaccination. In another controlled study by our group, we showed that 72% of cancer patients undergoing chemotherapy without rituximab achieved protective immunity after influenza vaccination, compared with 87% in the control group.⁸  Among lymphoma patients, 38% had a sero-protective response. This is in line with results from a number of studies demonstrating that lymphoma patients treated with chemotherapy without rituximab can respond to influenza vaccination but probably not as frequently as healthy controls.^7,9,10  These data and the fact that none of the patients in our study who received single-agent rituximab achieved sero-protection strongly suggest that the reason for nonresponsiveness in our patient group is B-cell depletion caused by rituximab. We cannot exclude disease status as a contributing factor to these poor responses. However, a previous study showed that the majority of lymphoma patients not undergoing any treatment responded to influenza vaccination.⁷  Another confounding factor may be that the median age of the patients was higher than among controls (63 vs 47 years). Data from a recent meta-analysis, however, concluded that adequate sero-protection against influenza A H1N1 was achieved in all age groups, except children younger than 3 years even after 1 dose.¹⁶  Some studies with limited patient numbers have suggested that rituximab has a negative impact on response to influenza vaccine, both during treatment^12,13  and more than 6 months after treatment.¹⁴  Takata et al found that in 7 non-Hodgkin lymphoma patients treated with rituximab and CHOP, none developed protective antibody titers against influenza primary antigen for the 2005-2006 seasonal vaccine,¹²  and van der Kolk et al reported a reduced immune response after rituximab therapy in 11 patients.¹³  Bedognetti et al found significantly lower responses to the 2008-2009 seasonal vaccine in 31 non-Hodgkin lymphoma patients treated with rituximab-containing regimens.¹⁴  Unlike our study, these 31 patients had completed treatment 6 months or more before vaccination.¹⁴ 

The present study represents the first large controlled study aimed to investigate humoral responses to influenza vaccination in lymphoma patients treated with rituximab as a single agent or in combination with chemotherapy. No vaccine-induced protective immunity was observed in any cases against the influenza A (H1N1) 2009 (“swine flu”) virus. The data strongly suggest that patients treated with rituximab cannot be expected to achieve protection to the same degree as healthy persons, and should thus be given anti–viral agents when infection is suspected, in addition to greater precautions to other protective measures, such as household vaccination and hand hygiene. Patients with non-Hodgkin lymphoma often receive rituximab as part of induction treatment, at relapse, and also as long-term maintenance therapy.^17,18  It is important to be aware that such patients may fail to respond adequately to not only influenza vaccinations but also other common vaccines.

The authors thank Berit Sandstad for statistical support and the laboratory unit for flow cytometry at the Clinic for Diagnostics and Intervention, Department of Pathology, Oslo University Hospital, for flow cytometric analyses.

Contribution: O.E.Y., D.T., and A.K. designed the study, provided data, analyzed data, and wrote the paper; O.H. and K.W. performed laboratory analyses and wrote the paper; A.T., S.D., and A.K. performed laboratory analyses; and K.F.W., B.Ø., R.E., T.N., and P.M. provided data and wrote the paper.

Conflict-of-interest disclosure: The authors declare no competing financial interests.

Correspondence: Olav Erich Yri, Oslo University Hospital, Radiumhospitalet, PO Box 4953, Nydalen, 0424 Oslo, Norway; e-mail: olav.yri@rr-research.no.