Background. To better establish the value of vaccination against influenza viruses, we estimated vaccine-averted influenza illnesses among young children and older adults in Chile, Guyana, and Paraguay. Methods. We gathered country- and target population-specific data on monthly influenza hospitalizations, vaccine coverage, and vaccine effectiveness from surveillance records and immunization registries during 2013-2018. We applied a static compartmental model to estimate differences in the number influenza-associated respiratory disease events (symptomatic nonhospitalized illnesses, medically attended illnesses, hospitalizations) in the presence and absence of influenza vaccination programs. Results. Between 2013 and 2018, vaccinating 68% of children aged 6-23 months in Chile averted an annual mean of 14 617 nonhospitalized, 9426 medically attended, and 328 hospitalized influenza illnesses; vaccinating 28% of children aged 6-23 months in Paraguay averted 1115 nonhospitalized, 719 medically attended, and 25 hospitalized influenza illnesses. Vaccinating 59% of older adults in Chile averted an annual mean of 83 429 nonhospitalized, 37 079 medically attended, and 1390 hospitalized influenza illnesses; vaccinating 36% of older adults in Paraguay averted an annual mean of 3932 nonhospitalized, 1748 medically attended, and 66 hospitalized influenza illnesses. In Guyana, a hypothetical campaign vaccinating 30% of children aged <5 years could have prevented an annual 1496 nonhospitalized, 971 medically attended, and 10 hospitalized influenza illnesses. Vaccinating 30% of adults aged >= 65 years could have prevented 568 nonhospitalized, 257 medically attended, and 10 hospitalized influenza illnesses. Conclusions. Influenza vaccination averted tens of thousands of illnesses and thousands of hospitalizations in Chile and Paraguay; influenza vaccination could have had a proportional benefit in Guyana.