OBJECTIVES: New influenza vaccines were developed to improve vaccine effectiveness by expanding influenza B coverage and boosting hemagglutinin (HA) concentration.  This research aims to assess the health impact of the new vaccines – high dose (HD) and quadrivalent influenza vaccines (IIV4), instead of IIV3, in adults aged 65 and older under Ontario’s Universal Influenza Immunization Program (UIIP).   METHODS: An analytical model of one flu season was developed using Ontario’s physician visits and ED uses, and Canadian influenza hospitalization and mortality rates with three age cohorts (age 65-74, 75-84, and 85 and above) at two levels of health risks (high and low).  Ontario’s demographic data was from Statistics Canada.  Vaccine efficacy and effectiveness against health outcomes were based on published studies.  Sensitivity analyses with extreme values of all relevant parameters were conducted.   RESULTS: Use of HD in place of IIV3 would avert 13,271 influenza cases (range: 4,648-23,161) and 2,483 symptomatic non-consulting cases (range: 690-5,226) annually, and decrease health care utilization significantly – 3,818 physician office visits (range: 1,530-5,520), 1,223 emergency department (ED) uses (range: 485-1,786), 772 hospitalizations (range: 442-1,223) and 341 deaths (range 195-537).  These reductions in health outcomes would avoid 857 outpatient antiviral treatments (range: 0-2,192) and eliminate 4,546 days of lost productivity (range: 1,387-10,054) among Ontario’s elderly residents a year.  IIV4 also showed a reduction in influenza-related health outcomes – 4,900 influenza cases (range: 3,364-11,817), 1,178 symptomatic non-consulting cases (range: 499-2,665), with 102 hospitalizations (range: 51-175) and 33 deaths (range 17-57) avoided annually; as a result, 1,623 (623-3,928) work days loss were prevented.   CONCLUSIONS: Although potential net health impact would fluctuate annually depending on the variability of influenza viruses, both HD and IIV4 are expected to attain significant to modest reductions in influenza-associated morbidity and mortality in seniors.  Those findings were proven to be robust in sensitivity analyses.