Corrigendum: Mucosal and Systemic Immune Responses to Influenza H7N9 Antigen HA1–2 Co-Delivered Intranasally With Flagellin or Polyethyleneimine in Mice and Chickens - Song, Li; Xiong, Dan; Song, Hongqin; Wu, Lili; Zhang, Meihua; Kang, Xilong; Pan, Zhiming; Jiao, Xinan (Frontiers in Immunology, 2018)