Relative Effectiveness of Egg- vs Cell-Based Quadrivalent Influenza Vaccines in Periods of Increased Influenza Activity

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Researchers conducted a study to compare the relative effectiveness of egg-based vs cell-based quadrivalent influenza vaccines in decreasing hospitalizations and emergency department admissions during influenza season.

The following article is a part of conference coverage from the IDWeek 2021, being held virtually from September 29 to October 3, 2021. The team at Infectious Disease Advisor will be reporting on the latest news and research conducted by leading experts in the field. Check back for more from the IDWeek 2021.

During either a period of increased influenza activity or a general influenza season, a retrospective cohort study found that a quadrivalent cell-based influenza vaccine (QIVc) was associated with a greater decrease in hospitalizations and emergency department (ED) admissions compared with a quadrivalent egg-based influenza vaccine (QIVe-SD). These findings were presented at IDWeek, held virtually from September 29 to October 3, 2021.

During influenza vaccine production, the egg- or cell-based preparations effect the influenza hemagglutinin protein, which may subsequently decrease the effectiveness of the vaccine. It remains unclear what impact the phenomenon of egg adaptation has on real-world healthcare outcomes.

Participants aged 4 to 64 years who were vaccinated with either QIVc (n=1,150,134) or QIVe-SD (n=3,924,819) formulation were enrolled and assessed for rates of influenza- or respiratory-related hospitalizations or ED admissions between August 2019 and March 2020. The period of increased influenza activity was defined as December 8, 2019 to March 7, 2020. Data were sourced from the IQVIA PharMetricsâ Plus database.

The investigators found that the QIVc formulation was associated with significantly increased relative vaccine effectiveness compared with QIVe-SD in regard to influenza-related (inverse probability of treatment weighting [IPTW], 5.3%; 95% CI, 0.5%-9.9%) and respiratory-related (IPTW, 8.2%; 95% CI, 6.5%-9.8%) hospitalizations or ED admissions.

During the defined period of increased influenza activity only, a similar pattern was observed, in which participants who received the QIVc formulation had increased relative vaccine effectiveness against influenza-related (IPTW, 5.7%; 95% CI, 0.8%-10.4%) or respiratory-related (IPTW, 7.3%; 95% CI, 5.4%-9.2%) hospitalizations or ED admissions.

This study was limited because data collection was suspended prematurely due to the COVID-19 pandemic.

The investigators, who were consultants or employees of Seqirus, concluded that the cell-based influenza vaccine formulation was more effective at decreasing hospitalization or ED admissions than the egg-based formulation during both a period of increased influenza activity or general influenza season.

Disclosure: Some author(s) declared affiliations with industry. Please refer to the original article for a full list of disclosures.


Divino V, Postma M, Pelton SI, et al. Relative vaccine effectiveness against influenza-related and any respiratory-related hospital encounter during the 2019/20 high influenza activity period: A comprehensive real-world analysis to compare quadrivalent cell-based and egg-based influenza vaccines. Presented at: IDWeek; September 29 to October 3, 2021. Poster 96.

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