Is Flu Vaccine Safe for Cancer Patients Receiving Immune Checkpoint Inhibitors?

A recent report describes a high rate (52%) of new-onset immune-related adverse events (IRAEs) in cancer patients who receive seasonal inactivated influenza vaccine while also receiving anticancer therapy with an immune checkpoint inhibitor (ICI; J Immunother Cancer 2018; 6:40). Because ICIs are monoclonal antibodies that restore some T-cell–mediated immune responses, they raise concerns that patients receiving these agents may have adverse immune responses to the flu vaccine.

To examine this issue, investigators at a tertiary-care institution conducted a retrospective review of 370 cancer patients who received a flu vaccine within 65 days of ICI therapy for 3 consecutive seasons beginning in 2014; most patients received an anti-PD-1 ICI (pembrolizumab or nivolumab). The median duration of ICI treatment was 139 days. The main cancer types were lung (46%) and melanoma (19%).

At median follow-up of 512 days, there was no increase in the incidence or severity of IRAEs in these patients compared with historical studies of cancer patients taking ICIs who did not receive the flu vaccine. Overall, 20% of patients developed IRAEs; of these, 7% were grade 1 (mild) IRAEs, 53% were grade 2 (moderate), 36% were grade 3 (severe), 4% were grade 4 (life-threatening), and none were grade 5 (death). The main IRAEs were endocrine (28%), pneumonitis (25%), colitis (13%), and transaminitis (12%). IRAEs were more common among patients who received other ICIs besides anti-PD-1 drugs. Most IRAEs occurred in patients who were older and, therefore, had received the trivalent high-dose vaccine. Of note, the incidence of laboratory-confirmed influenza among the study cohort during the 3 seasons was 3.5%, while the institution-wide incidence was 10.7%.