ReviewInfluenza vaccination in adult patients with solid tumours treated with chemotherapy

- Influenza A and B infection causes significant morbidity and mortality in adult patients with solid tumours.
- Guidelines recommend annual vaccination with the inactivated influenza vaccine (IIV) in patients treated with chemotherapy.
- IIV reduces pneumonia, mortality and results in fewer interruptions of chemotherapy in patients with colorectal carcinoma.
- Serological efficacy of IIV was demonstrated in 20 studies in adult patients with solid tumours receiving chemotherapy.
- The minimum level of antibodies associated with protection (seroprotection) can be achieved in the majority of patients.
- No safety concerns have been identified with the inactivated influenza vaccine in cancer patients.
- IIV is an effective and safe measure to reduce influenza-related complications in adult patients regardless of chemotherapy.

Patients with solid tumours receiving chemotherapy are at risk for influenza complications. Yearly influenza vaccination is recommended to patients treated with chemotherapy. However, adherence to vaccination is low, most likely due to lack of data on efficacy, optimal timing and safety of vaccination. There is scarce evidence for the effectiveness of the influenza vaccine in adult patients with solid tumours and chemotherapy on reduction of pneumonia, decreased mortality and fewer interruptions of oncological treatment. A review of 20 non-randomised serological studies in adult patients with different cancer types and chemotherapy provides insight in general trends of response to vaccination. Overall, the magnitude of the antibody response after influenza vaccination (i.e. seroconversion) can be lower than in healthy controls, but the majority of patients with solid tumours is able to mount a timely, protective immunological response (i.e. seroprotection) regardless of chemotherapy schedule, similar to healthy controls. Small sample sizes, patient heterogeneity and lack of comparable study designs limit more specific recommendations related to cancer type and optimal timing of vaccination. The inactivated influenza vaccine is safe to administer to immunosuppressed patients; side-effects are similar to those in healthy individuals. Although vaccination before start of chemotherapy is preferred to ensure optimal protection in adults with solid tumours, also vaccination during chemotherapy can reduce influenza-related complications considering the overall trends in serological response. Given the increased morbidity and mortality of influenza, influenza vaccination should be advocated as an inexpensive and safe preventive measure in patients with solid tumours receiving chemotherapy.