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

Hibino, Makoto; Kondo, Tetsuri

We performed a systematic search of PubMed and the Cochrane library to identify published reports on interstitial pneumonia associated with the influenza vaccine. Interstitial pneumonia is a rare complication of the influenza vaccine and was first described in association with this vaccine in 1998 (6) . Our search identified 9 cases (5 men and 4 women; mean age, 62.2 years; age range, 38-75 years) of influenza vaccine-induced interstitial pneumonia, including the present 2. Three were associated with a vaccine without the A(H1N1)pdm09-like antigen (6) (7) (8) and six with a monovalent influenza A(H1N1)pdm09 vaccine or a vaccine containing the A(H1N1)pdm09-like antigen (9) (10) (11) (12) . Two patients had pre-existing interstitial pneumonia, chronic hypersensitive pneumonia, and idiopathic pulmonary fibrosis. Almost 50% of the patients were former smokers. Eight patients exhibited fever and some respiratory symptoms, including cough or dyspnea on exertion. The mean interval between symptom onset and vaccination was 3.25 (range, 1-7) days, while the median interval between vaccination and diagnosis was 10 (range, 2-41) days. Chest computed tomography was performed for seven patients: consolidations and groundglass opacities were found in both lungs of six patients and only ground-glass opacities in both lungs of one. The lesion distribution varied among cases, including diffuse, predominantly peribronchovascular, and predominantly subpleural. Bronchofiber examination was performed for five patients. BALF examination revealed lymphocytosis and eosinophilia in three patients and only lymphocytosis in one. Transbronchial lung biopsy showed lymphocytic interstitial inflammation in four patients and/or organizing pneumonia (granulation tissue plugs within airspaces) in three. DLSTs, performed using peripheral blood lymphocytes for four patients and BALF lymphocytes for one, showed positive results. Eight patients were treated with systemic corticosteroids at varying initial doses, and three received steroid pulse therapy. Three patients-one pregnant woman and two with preexisting interstitial pneumonia-required mechanical ventilation support. All nine patients survived, indicating a good prognosis.