In record speed, vaccines are here, and more are on their way. Less than a year since the coronavirus began ravaging the world, the first shots are raising hopes for wiping the COVID-19 pandemic from the face of the earth.

Today’s programs in the U.S. and the U.K. are precursors to immunization campaigns intended to reach the planet’s entire population — all 8 billion people in every corner of the globe.

There is reason for optimism. Vaccines are the best, and perhaps only, way to eliminate infectious disease: Smallpox has been eradicated and polio is on the brink, with just two countries where transmission persists. But global vaccine campaigns take time — usually decades — suggesting that even with the latest technologies, money and might behind the unprecedented global drive to knock out COVID-19, the disease is unlikely to be eliminated any time soon.