Immunogenicity and safety of a trivalent inactivated influenza vaccine produced in Shenzhen, China versus a comparator influenza vaccine: a phase IV randomized study

Seasonal influenza causes substantial morbidity and mortality in China, which largely results from limited vaccine accessibility and poor vaccination coverage. Since 2013, Sanofi Pasteur’s facilities in Shenzhen, China have produced a trivalent inactivated influenza vaccine (Shz-IIV3) for each influenza season according to Chinese pharmacopeia requirements. However, the immunogenicity of Shz-IIV3 has not been compared to existing Chinese trivalent inactivated influenza vaccines (IIV3s). Here, we describe the results of a phase IV, observer-blind, randomized study to evaluate whether the immunogenicity of Shz-IIV3 was non-inferior to a comparator IIV3 (Hualan Biological Engineering Inc) also manufactured and licensed in China. Healthy adults aged 18−59 years were randomly assigned in a 1:1 ratio to receive a single 0.5-mL intramuscular injection of the 2017–2018 Northern Hemisphere formulation of Shz-IIV3 (n = 800) or the comparator IIV3 (n = 799). Between baseline and day 28 after vaccination, hemagglutination inhibition titers for the three vaccine strains increased by at least 4-fold and were of similar magnitude in Shz-IIV3 and comparator IIV3 recipients. The rate of seroconversion or significant increase in titers was 62% to 92% in Shz-IIV3 recipients, and 63% to 91% in comparator IIV3 recipients. Post-vaccination hemagglutination inhibition titers and seroconversion rates for Shz-IIV3 were statistically non-inferior to the comparator IIV3 for all three influenza vaccine strains. Rates of solicited and unsolicited vaccine-related adverse events were similar between the two vaccine groups. These results demonstrated that Shz-IIV3 was as immunogenic and safe in adults as a comparator Chinese IIV3, and support the continued use of Shz-IIV3 in China.