Nazir Ahmed stands on a hilltop in the Indian territory of Jammu and Kashmir gazing at the rolling green landscape that unfolds before him. The health-care worker scans a nearby valley, searching for shepherds tending their sheep by the meandering branches of the river below. Dangling by his side is a bright blue cooler, a vibrant reminder of Ahmed and his team's urgent task: Deliver as many COVID-19 vaccinations as possible.

The team is among many groups who are trekking, boating, dogsledding, and more to deliver vaccines to people in the most remote corners of the world. No matter how secluded, all communities are at risk from the deadly virus. The question is not if it will arrive: "The virus has