BACKGROUND:
Cancer patients are at a higher risk for developing influenza (flu) related complications. It is unclear if the flu vaccine exacerbates immune events in patients treated with ICIs.
METHODS:
We conducted an IRB-approved retrospective review of advanced cancer patients on ICIs who received the flu vaccine during three consecutive seasons; 2014-15, 15-16, and 16-17. The primary outcome assessed was any "new onset" immune-related adverse event (IRAE). A subset analysis of vaccinated patients newly treated with anti PD-1 agents (nivolumab or pembrolizumab) was conducted to assess overall IRAE rates for comparison with published clinical trials.
RESULTS:
During the three seasons, 370 patients met criteria for ICI and vaccination within ~ two months (65 days). The most common underlying cancers were lung (46%) and melanoma (19%); 61% of patients received anti PD-1 agent only. In the entire cohort, 20% experienced an IRAE (any grade); incidence of grade 3 or 4 toxicity was 8%. No grade 5 events occurred. In the subset of 170 patients newly treated with anti PD-1 agents, overall IRAE rate was 18%, grade 3/4 events occurred in 7.6%. Influenza was diagnosed in 2 patients.
CONCLUSION:
No increase in incidence or severity of IRAE was detected in patients on ICIs who received the inactivated influenza vaccine within ~ 2 months of ICI. For newly treated patients on anti-PDI agents, IRAE rates were comparable to published clinical trials and did not vary with order of administration. Routine seasonal flu vaccination is encouraged in patients on ICIs.