The world is experiencing the most dramatic increase in human longevity seen in history. By 2050, adults over age 65 will make up over one-sixth of the global population, while the number over age 80 will triple to 426 million. Yet this increasing longevity does not mean good health. From infectious diseases like COVID-19 to chronic conditions like cancers and Alzheimer’s, the globe is facing a staggering increase in disease burden over the coming decades. Underlying this is the age-related decline of the immune system, which limits our ability to fight disease and undermines the effectiveness of vaccines and therapeutics. New technologies such as AI and machine learning are now enabling scientists for the first time to understand this decline in immune function. This has the potential to revolutionize our ability to develop effective drugs and vaccines for older adults. The Human Immunomics Initiative (HII) was founded to drive forward research on this critical question. Joining together the Harvard T.H. Chan School of Public Health and the Human Vaccines Project, one of the leading human immunology research efforts, HII will seek to extend healthy life spans by determining the underlying rules of human immunity, with a focus on older adults. Together, we’re unlocking possibilities for lives that are not just longer, but also healthier.