Surveillance of the current situation regarding influenza vaccination according to medical oncologists in Japan.

This study aimed to clarify the attitude of oncologists toward influenza vaccination and the current situation and issues regarding influenza vaccination for patients on chemotherapy in Japan. A web-based survey of medical oncologists certified by the Japanese Society of Medical Oncology was conducted between November 1 and December 31, 2019. Of the 1,369 medical oncologists who were invited to participate, 415 (30.3%) responded to our survey. The questionnaire comprised four sections: "oncologist characteristics," "oncologist attitude towards influenza vaccines and the current status of influenza vaccination for cancer patients undergoing chemotherapy," "incidence of influenza infection and associated treatment complications," and "treatment policy for influenza infection." One hundred fifty-three (36.9%) physicians replied that they did not actively encourage influenza vaccination for patients undergoing chemotherapy. The primary reasons given were lack of evidence (48/153, 31.4%) and uncertainty of appropriate timing (46/153, 30.1%). There was diverse variation in the timing of vaccination and in the levels of encouragement based on the cancer location and medication type. Two hundred eighty-three (68.2%) oncologists reported that their cancer patients had experienced influenza infection while undergoing chemotherapy, and 169 (40.7%) responded that their patients had experienced an administration delay or discontinuation of medication because of influenza infection. Our surveillance revealed some oncologists considered evidence regarding the administration of influenza vaccine to cancer patients undergoing chemotherapy (particularly the optimal timing and level of recommendation by cancer location and medication) to be lacking. It also exposed the adverse impact of influenza infection in cancer patients.