Although the influenza vaccine is relatively safe and effective, serious complications can develop in rare cases. We encountered two cases of interstitial pneumonia that developed after vaccination during the 2014-2015 influenza season. Overall, nine cases, including the two presented here, have been recorded in PubMed and the Cochrane library; eight patients were treated with corticosteroids, and all nine survived, suggesting a good prognosis. Interstitial pneumonia is rare; however, we found an increase in its incidence after 2009. Therefore, clinicians must be aware of the possibility of this complication and duly educate all patients in advance.