OBJECTIVE Influenza virus infection has significant morbidity and mortality in patients with medical co-morbidities who are also immunosuppressed. The efficacy of the seasonal influenza vaccine has not been well studied in patients receiving chemotherapy. We assessed the efficacy of seasonal influenza vaccine in patients with non-haematological malignancy on active treatment (chemotherapy and targeted therapy). METHODS A prospective single arm, open label study with 53 patients with non-haematological cancers recruited during the 2011 and 2012 influenza seasons. Participants had one dose of 2011/2012 trivalent vaccine containing strains A/California/7/2009(H1N1), A/Perth/16/2009 (H3N2) and B/Brisbane/60/2008 (Fluvax) prior to or in-between treatment cycles. Haemagglutination inhibition antibody (HIA) titres in serum were measured at baseline 3, 6 and 24 weeks. Primary endpoint: seroconversion rate (SCR) at 3 weeks. Secondary endpoints: late SCR at 6 weeks. rate of sustained sero-protection titres (SPR) at 24 weeks. Seroconversion was defined as postvaccination ≥ 4-fold increase in HIA titre and sero-protection defined as a HIA ≥ 1:40. RESULTS The SCR at 3 weeks were 35%, 30% and 22.5% to the H1N1, H3N2 and B/Bris strains, respectively. There were no new cases of late SC at 6 weeks or 24 weeks. The SPR at 3 weeks were 72.5%, 65% and 40%, respectively, to H1N1, H3N2 and B/Bris. The SPR at 24 weeks to H1N1, H3N2 and B/Bris were 40%, 52.5% and 17.5%, respectively. CONCLUSIONS Patients on various solid tumour treatments achieve sero-protection rate congruent with the general population. The sero-protection HIA titres were not sustained at 24 weeks postvaccination.