 The 2017-18 winter flu season in Hong Kong was dominated by influenza beat Yamagata, and we found that the overall vaccine effectiveness, VE, against all influenza was 59.1 percent, 95 percent C.I. 41.1 to 71.8 percent, using a test negative case control design with respiratory specimens and clinical information from patients with influenza-like illness. The seasonal flu vaccine provided moderate to good protection against laboratory-confirmed influenza infection at primary care level in Hong Kong during the 2017-18 winter influenza season. This article was authored by young Y. Desmond Chan, Mai Yuling Wang, K.A. Wing A.U., and others.