Effectiveness of cell-based vaccines against influenza


Deborah Molrine, MD, Clinical Program Director, QIVc at CSL Seqirus, discusses CSL Seqirus’ cell-based quadrivalent seasonal influenza vaccine, along with the effectiveness of cell-based vaccines in children.

In a Q&A, Deborah Molrine, MD, clinical program director, QIVc at CSL Seqirus, discussed the now available FLUCELVAX QUADRIVALENT vaccine in children, along with general information on influenza and vaccine types.

Q: How does influenza affect children aged 6 months to 5 years compared to older patients?

A: Children under the age of 5 years represent one of the high-risk groups for flu-related complications. Although flu seasons vary in severity, the US Centers for Disease Control and Prevention (CDC) reports that each year thousands of young children are hospitalized for flu, and although relatively rare, some children die from influenza each year. Importantly, about 80% of reported flu-related deaths occurred in children who were not fully vaccinated. Although influenza is often a self-limited illness, influenza-related complications observed in young children include otitis media, respiratory tract diseases such as bronchiolitis or pneumonia, myositis, myocarditis, and central nervous events such as seizures, meningitis, or encephalitis.

Q: What makes cell-based vaccines advantageous to other vaccines?

A: Influenza viruses may undergo changes when they are grown in eggs for vaccine production; such egg adaptation may result in the vaccine strains being less well-matched to virus strains circulating during the influenza season. Influenza viruses grown in a mammalian cell culture system avoid egg adaptation, providing a closer match to wild-type viruses. In seasons where egg adaptation occurs, studies suggest cell-based influenza vaccines have the potential to be more effective than traditional, egg-based influenza vaccines. There are also data that suggest if the first exposure of a child to influenza is from an egg-adapted vaccine, antibody responses are often elicited to epitopes that are not present on wild-type viruses. Even with future vaccinations, the immune response is directed to the initial egg-adapted epitopes, and such immune priming may result in less protective responses in subsequent influenza seasons.

Q: Where will the CSL Seqirus’ influenza vaccine go from here?

A: FLUCELVAX QUADRIVALENT is now available for all eligible persons 6 months of age and older. With this expanded age indication, we can better protect all eligible persons from the flu and flu-related illness with this influenza vaccine. According to the Centers for Disease Control and Prevention, during the 2019/20 US influenza season, an estimated 46,000 influenza-related hospitalizations occurred in children under 18 years of age and there were 199 deaths reported in children with laboratory-confirmed flu infection.1 We will continue to invest in both our adjuvant and cell-based technologies to provide effective protection against influenza for as long as demand exists.

Q: What do you consider to be the most important piece of data from this trial?

A: The most important piece of data from this trial confirms for the first time that a cell-based quadrivalent inactivated influenza vaccine (QIVc) is safe and well-tolerated in the youngest pediatric population for whom immunization is recommended. The vaccine elicited antibody responses that were of similar magnitude to those produced by a previously licensed vaccine for this age group and thus expected to be effective.

Q: Is there anything you would like to add?

A: As the flu season is upon us, vaccination is the best intervention to protect all persons starting at 6 months of age from getting sick with the flu. The burden of illness is especially high in young children. It’s important to speak with your child’s healthcare provider and schedule an appointment to get vaccinated. FLUCELVAX QUADRIVALENT is now approved for all eligible people 6 months and older.


1. Estimated flu-related illnesses, medical visits, hospitalizations, and deaths in the United States — 2019–2020 flu season. Centers for Disease Control and Prevention. Updated October 7, 2022. Accessed October 18, 2022. https://www.cdc.gov/flu/about/burden/2019-2020.html#:~:text=The%20overall%20burden%20of%20influenza,related%20deaths%20(Table%201).

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