The pandemic H1N1 influenza vaccine results in low rates of seroconversion for patients with hematological malignancies.

Patients with hematological malignancies are at increased risk of influenza and its complications, but evidence for the efficacy of influenza vaccination in this population is limited. We sought to determine whether patients being treated for hematological malignancies were able to mount protective antibodies to the H1N1 influenza vaccine. Pre- and post-vaccination plasma samples were collected from patients with hematological malignancies during the 2009-2010 influenza season. Seroconversion was defined as a four-fold increase in antibody titer, as measured by the hemagglutinin inhibition test. Sixty-two patients received the H1N1 vaccine and 41 patients were unvaccinated controls. The rate of seroconversion among vaccinated patients was 21%, which was significantly higher than that in unvaccinated patients (0%), but significantly lower than that previously reported for healthy adults. Physicians should be aware that influenza vaccination may not generate an immune response in patients with hematological malignancies. Larger studies are required to confirm these results.