Vaccines are one of the great human accomplishments of the 20th century, a powerful weapon that has curtailed the spread of deadly and disabling diseases. They have led to an unprecedented improvement in both human life span and quality of life. But even best-in-class formulations can have limited efficacy, and vaccine side effects can create barriers to widespread adoption. Aaron Esser-Kahn, professor of molecular engineering, takes an engineering approach to this problem, creating better adjuvant designs that can provide safe, lasting protection. He will discuss recent progress in the field, and its implications for global health.