Auto-disable syringes are specially designed to prevent reuse because they automatically lock after the first plunge. They’re the gold standard for immunization campaigns in low- and middle-income countries and have drastically reduced the risk of contamination and spread of blood-borne diseases. But the pandemic has led to concerns about supply shortages amid the largest vaccination drive in human history. Manufacturers have been scaling up, but as The World’s Elana Gordon reports, ongoing logistical challenges highlight the complexities of global immunization efforts.