BACKGROUND: We conducted a phase I/II clinical trial to evaluate the safety and immunogenicity of a Madin-Darby canine kidney (MDCK) cell-grown inactivated H7N9 influenza vaccine for pandemic preparedness purposes.

METHODS: Between April 7, 2015 and May 27, 2016, healthy adults aged 20-60years were enrolled sequentially in phase I (n=40) and phase II (n=160) from three hospitals in Taiwan and randomized to receive 2 doses of whole-virus H7N9 vaccine (15 or 30μg hemagglutinin antigen (HA) with or without an aluminum hydroxide adjuvant) at 21-day intervals. Safety up to 180days and changes in hemagglutinin inhibition (HI) titers at 21days after each vaccination were determined.

RESULTS: Of the 200 randomized subjects, 193 (96.5%) received 2 doses of the study vaccine and were included in the intention-to-treat analysis for safety, and 190 (95%) were included in the per-protocol analysis for immunogenicity. Most adverse events were mild and transient; no death or vaccine-related serious adverse events were reported. Overall, higher immune responses were observed in the groups administered with 30μgHA formulation than in the other two groups administered with 15μgHA formulation. The highest immune response was observed in subjects who received 2 doses of the adjuvanted vaccine containing 30μgHA with HI titer, seroprotection rate, seroconversion rate, and seroconversion factor of 36.2, 64.6%, 64.6% and 5.7, respectively.

CONCLUSIONS: Our study demonstrated that the H7N9 influenza vaccine containing 30μgHA with aluminum hydroxide adjuvant was immunogenic and safe in adults aged 20-60years.