Patients commonly ask whether they should receive vaccinations. Their enquiries have two purposes; they want to know if vaccination is safe and if it is effective. Although vaccination may sometimes transiently raise the peripheral lymphocyte count, there is no evidence that it triggers an exacerbation of the CLL. On the other hand, patients with CLL should be regarded as immunodeficient as far as vaccination with live attenuated organisms is concerned and these should be avoided. A list of such vaccines is given in Table 1.
Vaccines that should be avoided in CLL
Vaccines that are permissible
Haemophilus influenzae type b
Patients with CLL respond very poorly to vaccination. Even newly diagnosed Rai stage 0 patients with normal serum immunoglobulins fail to mount a primary response against a previously unseen antigen though on repeated injection about half the patients are able to mount a secondary response at a level substantially less than in normal individuals . Vaccination studies in CLL have been comprehensively reviewed by Sinisalo . Over the past fifty years there have been numerous investigations of vaccination against Streptococus pneumoniae, Haemophilus influenzae type b, influenza, tetanus, diphtheria, mumps, and Salmonella typhi. In general antibody responses to vaccines have been weak. Protein vaccines have produced weak to moderate responses in up to 50% of patients, chiefly in early stage patients with normal serum immunoglobulin levels, but responses to polysaccharide vaccines have been virtually zero . There have been several attempts to enhance responses.
Histamine exerts a complex influence on the immune response via receptors on dendritic cells, macrophages and T and B lymphocytes. It is involved in the regulation or helper T cell polarity and through the type 2 histamine receptor interferes with regulatory T cell function . Attempts have been made to enhance antibody responses to vaccines using the H-2 antagonist, ranitidine. One such study used ranitidine 300mg twice daily for 90 days in an attempt to enhance antibody production to Haemophilus influenzae type B (Hib) conjugated to tetanus toxoid and influenza virus with vaccines given on day 0 and boosted on day 45. The study showed a significantly increased response rate of 90% compared with 43% for controls in patients receiving the ranitidine with the Hib vaccine though no significant difference could be seen for the influenza vaccine . Improved responses to the tetanus toxoid conjugated Hib vaccine against both Hib and tetanus were also reported following ranitidine treatment by an independent group, but ranitidine failed to induce any responses to an unconjugated pneumococcal polysaccharide vaccine. Patients receiving ranitidine had higher levels of interleukin-18, a proinfllammatory cytokine that induces T cells to produce -interferon .
The problem of poor response to polysaccharide vaccines can be partially overcome by conjugation to protein antigens. In the case of Hib, conjugation to tetanus toxoid is effective [36, 37]. For pneumococcal vaccines, conjugation to diphtheria CRM197 carrier protein produces an more effective vaccine capable of elliciting antibody responses in 40% of patients with CLL, most effectively in Binet stage A patients . Studies using this vaccine with ranitidine are awaited.
Patients with CLL undergoing splenectomy will almost certainly not benefit from vaccination with pneumococcal polysaccharide vaccines. Vaccination with the conjugated vaccine maight be tried, but prophylaxis with appropriate antibiotics should be considered mandatory.
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34. Sinisalo M. Responses to vaccine antigens in chronic lymphocytic leukaemia. Academic Dissertation. University of Tampere Medical School, Finland. 2008. Available at http://acta.uta.fi/pdf/978-951-44-7271-8.pdf
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36. Jurlander J, deNully Brown P, Skov PS et al. Improved vaccination response during ranitidine treatment, and increased plasma histamine concentrations, in patients with B cell chronic lymphocytic leukaemia. Leukemia 1995; 9:1902-9.
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