A cell-based option is an alternative to traditional, egg-based vaccines

There are several factors that impact vaccine effectiveness. One of them is strain mismatch, when circulating influenza strains do not match the WHO-selected strains contained in the vaccine, often due to antigenic drift or egg adaptation. Another factor can be characteristics of the vaccine recipient, such as health status and age.1-4

Antigenic Drift

After strain selection, circulating influenza virus strains have the potential to mutate, which can impact vaccine effectiveness.2

Egg Adaptation

Mutations are also introduced during egg-based influenza vaccine production. In order for human viruses to grow well in eggs, the HA must adapt to bind to avian receptors.1,3,4

Cell-based influenza vaccines avoid egg adaptation

Egg adaptation occurs when the HA in the vaccine strain selected by the WHO adapts to bind to avian receptors in order to grow in eggs. These changes may result in strain mismatch.1

A strain mismatch occurred in 6 of the 10 influenza seasons between 2010-2011 and 2019-2020* in the US; half of them were caused by egg adaptation in the vaccine strains during vaccine production.3-13

Some egg-adaptive mutations may cause HA to be antigenically different from the WHO-selected strains. †1,14,15

Flu vaccine egg-based vaccine production compared to cell-based vaccine production

Cell-based influenza vaccines are designed to produce an exact match to the WHO-selected strain.†1,14,16

HA=hemagglutinin WHO=World Health Organization
*Preliminary end of season estimates for the 2019-2020 influenza season by the Centers for Disease Control and Prevention
† Match to the WHO-selected strain(s) does not predict clinical effectiveness
† These graphics provide a simplified overview of the egg-based and cell-based influenza vaccine production processes
§ This depiction assumes the circulating strain matches the WHO-selected strain

A cell-based vaccine for prevention of seasonal influenza

Cell-based manufacturing is a different production process compared to traditional egg-based manufacturing, that avoids egg adaptation.1,14

How does vaccine effectiveness impact the burden of influenza?

Influenza impacts the lives of millions, and vaccine effectiveness in the US has varied considerably over the 10 most recent flu seasons.17,18

Learn more about the burden of influenzaNext screen

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Please see Important Safety Information and full US Prescribing Information on each vaccine's respective product page.

References: 1. Rajaram S, Boikos C, Gelone DK, Gandhi A. Influenza vaccines: the potential benefits of cell-culture isolation and manufacturing. Ther Adv Vaccines Immunother. 2020 8:2515135520908121. doi:10.1177/2515135520908121 2. Paules CI, Sullivan SG, Subbarao K, Fauci AS. Chasing seasonal influenza— the need for a universal influenza vaccine. N Engl J Med. 2018 378(1):7-9. doi:10.1056/NEJMp1714916 3. Skowronski DM, Janjua NZ, De Serres G, et al. Low 2012-13 influenza vaccine effectiveness associated with mutation in the egg-adapted H3N2 vaccine strain not antigenic drift in circulating viruses. PLoS One. 2014 9(3):e92153. doi:10.1371/journal.pone.0092153 4. Zost SJ, Parkhouse K, Gumina ME, et al. Contemporary H3N2 influenza viruses have a glycosylation site that alters binding of antibodies elicited by egg-adapted vaccine strains. Proc Natl Acad Sci USA. 2017 114(47):12578-12583. doi:10.1073/pnas.1712377114 5. Centers for Disease Control and Prevention. Update: Influenza activity— United States, 2010-11 season, and composition of the 2011-12 influenza vaccine. MMWR Morb Mortal Wkly Rep. 2011 60(21):705-712. 6. Ohmit SE, Thompson MG, Petrie JG, et al. Influenza vaccine effectiveness in the 2011-2012 season: protection against each circulating virus and the effect of prior vaccination on estimates. Clin Infect Dis. 2014 58(3):319-327. doi:10.1093/cid/cit736. 7. McLean HQ, Thompson MG, Sundaram ME, et al. Influenza vaccine effectiveness in the United States during 2012-2013: variable protection by age and virus type. J Infect Dis. 2015 211(10):1529-1540. doi:10.1093/infdis/jiu647 8. Gaglani M, Pruszynski J, Murthy K, et al. Influenza vaccine effectiveness against 2009 pandemic influenza A(H1N1) virus differed by vaccine type during 2013-2014 in the United States.   J Infect Dis. 2016 213(10):1546-1556. doi:10.1093/infdis/jiv577 9. Zimmerman RK, Nowalk MP, Chung J, et al. 2014-2015 influenza vaccine effectiveness in the United States by vaccine type. Clin Infect Dis. 2016 63(12):1564-1573. doi:10.1093/cid/ciw635 10. Jackson ML, Chung JR, Jackson LA, et al. Influenza vaccine effectiveness in the United States during the 2015-2016 season. N Engl J Med. 2017 377(6):534-543. doi:10.1056/NEJMoa1700153 11. Flannery B, Chung JR, Belongia EA, et al. Interim estimates of 2017-18 seasonal influenza vaccine effectiveness — United States, February 2018. MMWR Morb Mortal Wkly Rep. 2018 67(6):180-185. doi:10.15585/mmwr.mm6706a2 12. Flannery B, Kondor RJG, Chung JR, et al. Spread of antigenically drifted influenza A(H3N2) viruses and vaccine effectiveness in the United States during the 2018-2019 season. J Infect Dis. 2020 221(1):8-15. doi:10.1093/infdis/jiz543 13. Dawood FS, Chung JR, Kim SS, et al. Interim estimates of 2019-20 seasonal influenza vaccine effectiveness — United States, February 2020. MMWR Morb Mortal Wkly Rep. 2020 69(7):177-182. 14. Centers for Disease Control and Prevention. Cell-based flu vaccines. Accessed August 3, 2021. https://www.cdc.gov/flu/prevent/cell-based.htm 15. Subbarao K, Barr I. A tale of two mutations: beginning to understand the problems with egg-based influenza vaccines? Cell Host Microbe. 2019 25(6):773-775. doi:10.1016/j.chom.2019.05.012 16. Mabrouk T, Ellis RW. Influenza vaccine technologies and the use of the cell-culture process (cell-culture influenza vaccine). Dev Biol. 2002 110:125-134. 17. Centers for Disease Control and Prevention. Key facts about seasonal flu vaccine. Accessed September 9, 2021. https://www.cdc.gov/flu/prevent/keyfacts.htm 18. Centers for Disease Control and Prevention. Past seasons vaccine effectiveness estimates. Accessed September 24, 2021. https://www.cdc.gov/flu/vaccines-work/past-seasons-estimates.html