biostudies-literatureUnknownGaglani MKaiser Permanente Washington Research InstituteUniversity of MichiganNCATS NIH HHSNCRR NIH HHSBaylor Scott &amp; White HealthUniversity of PittsburghMarshfield Clinic Research InstituteUS Centers for Disease Control and PreventionNCIRD CDC HHSIntramural CDC HHS<h4>Background</h4>Estimates of annual effectiveness of influenza vaccination combine multiple vaccine types. Reports of brand/product-specific vaccine effectiveness (VE) of egg- and cell-culture based quadrivalent inactivated influenza vaccines (IIV4/ccIIV4) are limited.<h4>Methods</h4>Using an observational test-negative study design, we compared effectiveness of selected IIV4 and ccIIV4 products among outpatients enrolled in the US Flu VE Network from 2014-2015 to 2018-2019. We used multivariable logistic regression to estimate product- and age-group-specific absolute and relative effectiveness of recommended, age-appropriate vaccines against symptomatic laboratory-confirmed outpatient influenza. Relative effectiveness of ccIIV4 versus IIV4 products was estimated during two seasons fromClinical infectious diseases : an official publication of the Infectious Diseases Society of Americaciaf579https://www.ebi.ac.uk/biostudies/studies/S-EPMC12667161biostudies-literatureAbsolute 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.PMC12667161U01 IP000471UL1 TR000005UL1 TR001857U01 IP000466U01 IP001039U01 IP001037CC999999U01 IP000467U01 IP001038U01 IP000473U01 IP001035U01 IP001034U01 IP000474UL1 RR024153Phillips CHKim SSChung JRMurthy KZimmerman RKNguyen HQGaglani MDubrocq GMartin ETRaiyani CKing JPSmith MMonto ASNowalk MPBeeram MKiniry EFlannery Bda Graca BfalseAbsolute 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.<h4>Background</h4>Estimates of annual effectiveness of influenza vaccination combine multiple vaccine types. Reports of brand/product-specific vaccine effectiveness (VE) of egg- and cell-culture based quadrivalent inactivated influenza vaccines (IIV4/ccIIV4) are limited.<h4>Methods</h4>Using an observational test-negative study design, we compared effectiveness of selected IIV4 and ccIIV4 products among outpatients enrolled in the US Flu VE Network from 2014-2015 to 2018-2019. We used multivariable logistic regression to estimate product- and age-group-specific absolute and relative effectiveness of recommended, age-appropriate vaccines against symptomatic laboratory-confirmed outpatient influenza. Relative effectiveness of ccIIV4 versus IIV4 products was estimated during two seasons from2025-01-01T00:00:00Z2025 Oct2026-06-06T07:10:29.952Z2026-06-06T03:06:21.517ZS-EPMC126671614110288010.1093/cid/ciaf579