The CDC reports that 1.13 million Americans have died of COVID-19 through June of 2023. I use a model of the impact over the past three years of vaccines and private and public behavior to mitigate disease transmission during the COVID-19 pandemic in the United States to address two questions. First, holding the strength of the response of behavior to the level of daily deaths from COVID-19 fixed, what was the impact of vaccines on cumulative mortality from COVID-19 up through June 2023? And second, holding the pace of deployment of vaccinations fixed, what would have been the impact of stricter or looser behavioral responses to COVID-19 deaths on cumulative mortality from COVID-19 over this same time period? In answering the first question, I find that vaccines saved 748,600 lives through June 2023. That is, without vaccines, cumulative mortality from COVID-19 would have been closer to 1.91 million over this time period. In answering the second question, I find that behavioral efforts to slow the transmission of the virus before vaccines became widely administered were critical to this positive impact of vaccines on cumulative mortality. For example, with a complete relaxation of these mitigation efforts, vaccines would have come too late to have saved a significant number of lives. Earlier deployment of vaccines would have saved many lives. I find that marginal changes in the strength of the behavioral response to COVID-19 deaths within the range of those responses estimated with the model have a significantly smaller impact on cumulative COVID-19 mortality over this time period.