Although the value of vaccines for COVID-19 may seem obvious, government action and investment in vaccines have not been commensurate with the enormous scale of benefits they offer, argue Juan Camilo Castillo and colleagues in this Policy Forum. Since even one extra month of exposure to COVID-19 kills hundreds of thousands, reduces global gross domestic product (GDP) by hundreds of billions of dollars, and generates large losses to human capital by harming education and health, expanding vaccine capacity even further would generate substantial global benefits. Castillo et al. report results of two related exercises: estimating the global benefits from vaccine capacity already in place, and estimating the benefits of undertaking additional capacity investment starting now. "The enormous estimates from both exercises provide a wake-up call relevant for the current [and future pandemics]," they say. For example, the results suggest that investing now in expanding capacity for an additional annual 1 billion courses of vaccine could accelerate completion of widespread immunization by over 4 months, providing additional global benefits of $576 to $989 per course. "This dwarfs prices of $6 to $40 per course seen in deals with vaccine producers," they say. They urge governments and international organizations to contract with vaccine producers to further expand capacity and encourage measures - such as delayed second doses, lower-dose regimens, or provision of only one dose to those previously infected - to "stretch" existing capacity. "These proposals could have large potential benefits; thus, investigating their medical appropriateness is worthwhile," they say. To avoid the issue of some countries ending up with vaccine allocations that are not optimally matched to their needs, the authors advocate for steps including a cross-country vaccine exchange. Such a mechanism is under consideration by COVAX, a global initiative to promote access to COVID-19 vaccines.