Absolute and Relative Effectiveness of Cell- and Egg-based Quadrivalent Inactivated Influenza Vaccine Products from 2014-2015 to 2018-2019 seasons, U.S. Flu VE Network.
Level 4 - case-series / case-control
Observational test-negative case-control study
PubMed 41102880 · doi:10.1093/cid/ciaf579
What was done
Researchers used an observational test-negative design among outpatients enrolled in the US Flu VE Network across five influenza seasons (2014–2015 to 2018–2019). Multivariable logistic regression was used to estimate product- and age-group-specific absolute and relative vaccine effectiveness (VE) of egg-based (Fluarix Quadrivalent, Fluzone Quadrivalent, FluLaval Quadrivalent) and cell-culture-based (Flucelvax Quadrivalent / ccIIV4) inactivated vaccines against symptomatic laboratory-confirmed outpatient influenza. Relative effectiveness between ccIIV4 and IIV4 was assessed during 2017–2019 among individuals aged ≥4 years.
What was found
Across five pooled seasons, absolute VE was 32% for Fluarix IIV4 (received by 18% of vaccinated patients) and 37% for Fluzone IIV4 (received by 15%). Pooling two seasons (2017–2019), absolute VE was 30% for ccIIV4 (11% of vaccinated patients) and 30% for FluLaval IIV4 (28% of vaccinated patients). Absolute VE was lowest against influenza A(H3N2) compared to A(H1N1)pdm09 and B lineages, and point estimates were lowest in adults aged ≥50 years. Relative effectiveness differences between products were not statistically significant.
Why it matters
This evaluation adds multi-season, brand-specific comparative data showing that cell- and egg-based quadrivalent inactivated vaccines confer comparable outpatient clinical protection.
Limits
The total sample size, exact confidence intervals, and p-values are not reported in the abstract. Comparisons involving cell-based vaccines were limited to two seasons, and observational test-negative designs are subject to residual confounding.
Cited by
- supports The prior year's influenza vaccine was approximately 30% effective.