Immunogenicity and safety of concomitant administration of recombinant COVID-19 vaccine and quadrivalent inactivated influenza vaccine in Chinese adults: An open-label, randomized, controlled trial

Hum Vaccin Immunother. 2024 Dec 31;20(1):2330770. doi: 10.1080/21645515.2024.2330770. Epub 2024 Apr 11.


The immunogenicity and safety of the concomitant administration of recombinant COVID-19 vaccine and quadrivalent inactivated influenza vaccine (Split Virion) (QIIV) in Chinese adults are unclear. In this open-label, randomized controlled trial, participants aged ≥ 18 years were recruited. Eligible healthy adults were randomly assigned (1:1) to receive QIIV at the same time as the first dose of COVID-19 vaccine (simultaneous-group) or 14 days after the second dose of COVID-19 vaccine (non-simultaneous-group). The primary outcome was to compare the difference in immunogenicity of QIIV (H1N1, H3N2, Yamagata, and Victoria) between the two groups. A total of 299 participants were enrolled, 149 in the simultaneous-group and 150 in the non-simultaneous-group. There were no significant differences in geometric mean titer (GMT) [H1N1: 386.4 (95%CI: 299.2-499.0) vs. 497.4 (95%CI: 377.5-655.3); H3N2: 66.9 (95%CI: 56.1-79.8) vs. 81.4 (95%CI: 67.9-97.5); Yamagata: 95.6 (95%CI: 79.0-115.8) vs. 74.3 (95%CI: 58.6-94.0); and Victoria: 48.5 (95%CI: 37.6-62.6) vs. 65.8 (95%CI: 49.0-88.4)] and seroconversion rate (H1N1: 87.5% vs. 90.1%; H3N2: 58.1% vs. 62.0%; Yamagata: 75.0% vs. 64.5%; and Victoria: 55.1% vs. 62.8%) of QIIV antibodies between the simultaneous and non-simultaneous groups. For the seroprotection rate of QIIV antibodies, a higher seroprotection rate of Yamagata antibody was observed only in the simultaneous-group than in the non-simultaneous-group [86.0% vs. 76.0%, p = .040]. In addition, no significant difference in adverse events was observed between the two groups (14.2% vs. 23.5%, p = .053). In conclusion, no immune interference or safety concerns were found for concomitant administration of COVID-19 vaccine with QIIV in adults aged ≥ 18 years.

Keywords: Recombinant COVID-19 vaccine; concomitant administration; immunogenicity; quadrivalent inactivated influenza vaccine; safety.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Antibodies
  • COVID-19 Vaccines / adverse effects
  • COVID-19* / prevention & control
  • China
  • Humans
  • Influenza A Virus, H1N1 Subtype*
  • Influenza A Virus, H3N2 Subtype
  • Influenza Vaccines* / adverse effects


  • COVID-19 Vaccines
  • Influenza Vaccines
  • Antibodies

Grants and funding

This work was supported by Jiangsu GDK Biological Technology Co., Ltd (Taizhou, Jiangsu, P.R. China).