Interstitial Pneumonia Associated with the Influenza Vaccine: A Report of Two Cases

Hibino, Makoto; Kondo, Tetsuri

His medical history was unremarkable, and a chest roentgenogram obtained during a routine annual health check-up 7 months ago showed normal findings. On admission, his oxygen saturation was 93% in room air, and the other vital signs were normal. A physical examination revealed inspiratory fine crackles at both lung bases. A complete blood count revealed no abnormalities. Blood chemistry showed normal renal and liver function tests and an LDH level of 302 IU/L. Serological tests revealed the following: CRP, 2.95 mg/dL; ferritin, 701.1 ng/mL; sIL-2R, 670 U/mL; KL- 6, 2,276 U/mL; SP-D, 160.6 ng/mL; and SP-A, 152.9 ng/ mL. Chest roentgenography ( Fig. 2A) and computed tomography ( Fig. 2B) showed peripheral, predominantly basilar, and partially subpleural ground-glass opacities and consolidations without honeycomb changes in both lungs. The severe cough precluded carrying out pulmonary function tests. BALF examination revealed 49.3% lymphocytes, 15.5% eosinophils, 34.2% macrophages, and 1% neutrophils, without infectious organisms or malignant cells. The CD4 + /CD8 + ratio was 0.7. Transbronchial lung biopsy confirmed lymphocytic alveolitis and scattered granulation tissue plugs within airspaces (Fig. 2C) , with alveolar epithelial shedding and regenerative hyperplastic epithelia, suggesting organizing pneumonia with alveolar epithelial injury. A DLST performed using peripheral lymphocytes showed a positive reaction to the influenza vaccine, with a stimulation index of 330%.