A Case of Seasonal Influenza Vaccine-induced Pneumonitis Presenting with Multiple Pulmonary Nodules

A 39-year-old woman received a seasonal influenza vaccine in November 2015 and subsequently experienced malaise, low-grade fever, and chest discomfort. A chest X-ray performed 2 weeks after vaccination showed multiple nodular shadows in both lungs and ground-glass shadows in both lower lung fields. Her bronchoalveolar lavage fluid contained an unusually high number of lymphocytes, and a drug-induced lymphocyte stimulation test for seasonal influenza vaccine was positive. Transbronchial lung biopsy revealed the presence of granulomatous inflammation. Thereafter her abnormal chest shadow spontaneously improved. Based on these findings, the patient was diagnosed with drug-induced pneumonitis due to an influenza vaccine.