As a dangerous new virus began spreading around the globe in early 2020, The Bill & Melinda Gates Foundation turned to a tried-and-true playbook. It’s an approach that has worked well for the Seattle philanthropic giant for more than two decades, ever since it set out to boost childhood vaccinations in the developing world. Back then, the foundation helped bankroll a new, global entity — Gavi, The Vaccine Alliance — to broker deals with pharmaceutical companies, pool donations from wealthy countries and provide low-cost shots for the world’s poorest kids.