Preventing Influenza-Related Medical Encounters (US 2018-2019 Season): A Real-World Study from Seqirus™ and Veradigm®

Close-up of a person holding a syringe with someone's arm in the background
Thought Leadership  |  26 May 2021  |  By Joe Vasey, PhD

During the 2018-2019 influenza season in the United States, individuals aged four years and older who were vaccinated with cell culture-derived inactivated quadrivalent influenza vaccine (ccIIV4) had significantly fewer influenza-related medical encounters compared with individuals vaccinated with egg-derived inactivated quadrivalent influenza vaccines (eIIV4), according to a study conducted by Seqirus and Veradigm and published in Clinical Infectious Diseases.1

Real-world data for this non-interventional, retrospective cohort study of relative vaccine effectiveness were sourced from a large integrated dataset linking ambulatory patient electronic health records (EHRs)—Allscripts Touchworks® EHR, Veradigm EHR™, and Practice Fusion, available from the Veradigm HealthInsights database—with pharmacy and medical claims data. The study included over ten million individuals who had a record of receiving either ccIIV4 or eIIV4.

Influenza is a highly contagious respiratory infection, and the Centers for Disease Control and Prevention (CDC) recommend annual influenza vaccinations for individuals aged six months and older, particularly for those at high risk of serious complications. Approved in the US in 2016, ccIIV4 has been shown to have immunogenicity comparable to egg-derived vaccines.2

During the US 2018-2019 influenza season, egg-adaptive amino acid changes in the hemagglutinin protein of egg-derived viruses, identified within a subset of A(H3N2) viruses, were noted.3 Propagating influenza vaccine viruses in mammalian cells instead of in embryonated chicken eggs maintains viral antigenicity by eliminating opportunities for adaptive viral mutations to occur.4

Overall, the study supports the trend showing ccIIV4 may be more effective than eIIV4 during seasons characterized by egg-adaptive changes, during which influenza viruses derived from egg undergo mutations that affect antigenicity. The authors conclude that the study’s findings “provide further evidence supporting [cell-derived] ccIIV4 as a potentially more effective public health measure against influenza than an egg-derived equivalent.”


  1. Boikos C, Fischer L, O’Brien D, et al. Relative effectiveness of the cell-derived inactivated quadrivalent influenza vaccine versus egg-derived inactivated quadrivalent influenza vaccines in preventing influenza-related medical encounters during the 2018-2019 influenza season in the United States. Clin Infect Dis 2021;ciaa1944.
  2. Bart S, Cannon K, Herrington D, et al. Immunogenicity and safety of a cell culture-based quadrivalent influenza vaccine in adults: a phase III, double-blind, multicenter, randomized, non-inferiority study. Hum Vaccin Immunother 2016;12(9):2278-2288.
  3. Xu X, Blanton L, Elal AIA, et al. Update: influenza activity in the United States during the 2018-19 season and composition of the 2019-20 influenza vaccine. MMWR Morb Mortal Wkly Rep 2019;68:544-551.
  4. Boikos C, Sylvester GC, Sampalis JS, et al. Relative effectiveness of the cell-cultured quadrivalent influenza vaccine compared to standard, egg-derived quadrivalent influenza vaccines in preventing influenza-like illness in 2017-2018. Clin Infect Dis 2020;71:e665-e671.
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