In a Himalayan village in Kashmir, young health worker Masrat Farid packed her bag with vaccines on a frigid morning in January as strong winds swept snow through the air.

She is part of a team of health workers undertaking a door-to-door campaign in the region to deliver vaccine shots to teens and boosters to old people in remote mountain villages.

“We have to fight the infection. We have to keep going,” Farid said as she made her way through the knee-high snow in Gagangeer, a hamlet lying between forests.

Farid and her colleagues have vaccinated thousands in the last year, mostly in villages that they reach by trekking long distances across rugged countryside.