OBJECTIVES: Ontario, Canada, immunizes against influenza using a trivalent inactivated influenza vaccine (IIV3) under a Universal Influenza Immunization Program (UIIP). The UIIP offers IIV3 free of charge to all Ontarians over 6 months of age. A newly approved quadrivalent inactivated influenza vaccine (IIV4) offers wider protection against influenza B disease.  In this study, we explore the expected cost-utility and budget impact of replacing IIV3 with IIV4 within the context of Ontario’s UIIP. METHODS: We developed a model based on Ontario outcomes data published by Kwong and colleagues. We used Ontario based health care costs and Canadian based labor costs. Efficacy of IIV3 and IIV4 were estimated in a similar manner to a previous publication by Reed and colleagues. However, we improved by including emerging data from new meta-analyses on the efficacy of IIV3. These include new estimates of cross protection against mismatched B influenza offered by IIV3, as well as, new estimates of the vaccine efficacy in seniors. Conservatively, herd protection was not considered. RESULTS: Over an average influenza season, relative to IIV3, IIV4 is expected to avert an additional 2,516 influenza cases, 1,683 influenza-associated medical visits, 27 influenza-associated hospitalizations and 5 influenza-associated deaths. From a societal perspective IIV4 would generate 76 more QALYs and a net societal budget impact of $2,265,769.  The incremental cost effectiveness ratio (ICER) for this comparison was $29,738/QALY. 74% of simulations in a probabilistic sensitivity analysis were below $100,000/QALY and 29% were dominant. In a scenario analysis, the ICER was $94,248 per QALY from a third party payer perspective. CONCLUSIONS: IIV4 is expected to achieve reductions in influenza related morbidity and mortality compared to IIV3. Further, despite not accounting for herd protection IIV4 is still expected to be a cost effective alternative to IIV3.  Our conclusions were robust in the face of sensitivity analyses.