Synopsis: Influenza remains a morbid and life-threatening risk for patients with cancer, and prior studies have pointed to impaired response to vaccination as cause for serious concern. The current report details that lymphoma patients treated with the antibody rituximab, whether administered on its own or in conjunction with chemotherapy, saw markedly deficient immune responses to influenza vaccine treatments, with none of the 67 test patients achieving a protective titer, compared with 42 of 51 controls. Rituximab-treated lymphoma patients, then, are especially susceptible to influenza infection and vaccine failure. Infection prevention should especially be considered in the care of symptomatic patients, even those who have been appropriately vaccinated.
Source: Yri OE, et al. Rituximab blocks protective serologic response to influenza A (H1N1) 2009 vaccination in lymphoma patients during or within 6 months after treatment. Blood 2011;118:6769-6771.
Cancer patients’ concern about influenza is understandably heightened because their infection rates are considerably higher and mortality is four times more likely than in the general population. Cancer is itself immunosuppressive, so additional impairment from treatment and therapy is an important consideration. Lymphoma patients undergoing rituximab treatment in particular may be more susceptible to infection as this antibody can deplete B cells and impair humoral responses. As it has been established that rituximab treatment leads to impaired antibody responses to both carbohydrate and protein vaccines in patients with rheumatoid arthritis, it is similarly likely that lymphoma patients treated with rituximab have diminished vaccine response although this has not been confirmed.
In the current report, Yri and colleagues throughout Norway address this issue. Investigating antibody responses to the influenza A (H1N1) 2009 “swine flu” virus vaccine, Yri OE, et al tested a total of 67 lymphoma patients and 51 controls, all with low pre-vaccination titers, to determine rituximab’s effect on vaccine response. Each subject received the monovalent influenza A (H1N1) vaccine (Pandemrix; Glaxo SmithKline) and their antibody levels were measured before and three weeks or more after the vaccination through a standard hemagglutination-inhibition assay. For the purposes of the study, an antibody titer reading of greater than 40 was deemed protective. The patients were on average older than the controls, (mean age 63 years vs 47 years, respectively) and most of the patients had received a treatment of chemotherapy combined with rituximab; seven however, had received rituximab alone.
In the control group, only one showed no response, while eight had a titer of 20 and 42 of the 51 controls (82.4%) had a post-vaccination titer > 40. This stood in stark contrast to the vaccinated lymphoma patients, among whom only five persons had a vaccine titer of 20, whilst the remaining 62 patients had no detected titers at all. The sero-protection rate for this vaccine then, was 82% in controls but 0% in treated lymphoma patients.