RESUMEN
Israel was the first country to launch COVID-19 boosters, in late July 2021, with strong public health messaging. The booster campaign reversed rising infection rates from the Delta variant and reduced hospitalizations and deaths. The US booster rollout was slower, and public health messaging was mixed. We used the Israeli experience to ask the counterfactual question: How many lives could the US have saved if it had authorized boosters sooner? We estimated that through June 30, 2022, if the US had moved at Israel's speed and booster take-up percentages, it would have saved 29,000 lives. US regulatory caution, in the middle of a pandemic, thus had a large, avoidable cost. Yet the US booster rollout still avoided 42,000 deaths. Moving more slowly to approve boosters, as some advocated, would have cost many additional lives.