Absolute and Relative Effectiveness of Cell Culture-Based and Egg-Based Quadrivalent Inactivated Influenza (Flu)...

Estimates of the annual effectiveness of influenza vaccination combine multiple vaccine types. Reports of brand/product-specific vaccine effectiveness (VE) of egg-based and cell culture-based quadrivalent inactivated influenza vaccines (IIV4 and ccIIV4, respectively) are limited.

Using an observational test-negative study design, we compared the effectiveness of selected IIV4 and ccIIV4 products among outpatients enrolled in the US Influenza Vaccine Effectiveness (Flu VE) Network from 2014-2015 to 2018-2019. We used multivariable logistic regression to estimate the product-specific and age group-specific absolute VE and relative VE (rVE) of recommended, age-appropriate vaccines against symptomatic laboratory-confirmed outpatient influenza. The rVE of ccIIV4 versus IIV4 products was estimated during 2 seasons from 2017-2019 among participants aged ≥4 years.

Pooling data from 5 influenza seasons when 18% and 15% of vaccinated patients had received Fluarix Quadrivalent or Fluzone Quadrivalent IIV4, respectively, the VE against influenza was 32% for Fluarix and 37% for Fluzone. Pooling 2 seasons when 11% and 28% of vaccinated patients had received ccIIV4 (Flucelvax Quadrivalent) and IIV4 (FluLaval Quadrivalent), respectively, the VE against influenza for each product was 30%. The absolute VE compared with unvaccinated patients was lowest against influenza A(H3N2) compared with that against A(H1N1)pdm09 and each B lineage; VE point estimates were lowest among patients aged ≥50 years compared with 2 younger age groups. The rVE estimates were not statistically significant, indicating similar protection across vaccine products.

Comparisons of influenza vaccine products over multiple seasons showed benefit of both IIV4 and ccIIV4 against symptomatic laboratory-confirmed outpatient influenza, with similar absolute and relative levels of protection provided by each product.