Evaluation of pandemic H1N1 (2009) influenza vaccine in adults with solid tumor and hematological malignancies on active systemic treatment

Abstract Background Over 85% of healthy individuals vaccinated with the pandemic H1N1 (pH1N1) vaccine achieve seroprotection. Objectives We evaluated the safety and immunogenicity of pH1N1 vaccine in patients undergoing chemotherapy for hematological and solid tumor malignancies. Study design Adult patients, receiving chemotherapy undergoing pH1N1 vaccination at our institution had blood samples drawn for CBC (baseline only) and serology prior to and ≥21 days post vaccination. HAI antibody testing was performed for pH1N1 (A/California/7/2009 strain) and seasonal H1 (A/Brisbane/59/07 strain). Seroprotection was defined as a pH1N1 antibody titre ≥1:40 and seroconversion as an antibody titre >4× baseline. Patients completed a symptom diary card. Results Paired samples were available for 46 patients (20 solid tumor, 26 hematological), median age 56 (range 23–76) years. The seroprotective rate post-vaccination for solid tumors was 50% compared to 27% for hematological malignancy ( p  = 0.11), respective seroconversion rates were 45% and 19% ( p  = 0.06). In patients with solid tumors vaccination mid cycle resulted in the highest pH1N1 titres, although timing and blood count were not associated with seroconversion or seroprotection. For hematological patients, a normal leukocyte count and vaccination at the beginning of a cycle were associated with higher rates of seroconversion ( p  ≤ 0.05). Addition of rituximab to chemotherapy resulted in a failure to seroconvert ( p  = 0.05). Vaccination was well tolerated by all patients. Conclusions Although well tolerated, the seroprotection rate following pH1N1 vaccination is lower than that would be expected. Further investigation into immunization strategies in patients receiving chemotherapy is required.