Vaccination hesitancy, even in the midst of a global pandemic, is a major barrier to the elimination of several highly contagious and deadly diseases. While COVID-19 vaccines are getting the most attention, they are not the only vaccines that protect against deadly contagious diseases. And as with the COVID-19 vaccines, around the world, many communities are insufficiently covered by vaccines—particularly children. This is especially true in West Africa, where—though improving—childhood immunization rates still lag behind much of the world. To explore reasons for these persistent low childhood immunization rates, Breakthrough RESEARCH, a USAID-funded project that works to expand the evidence base for social and behavior change programming, increase healthy behaviors, and enable positive social norms through improved social and behavior change programming, conducted a study to look at behavioral drivers of decision-making about vaccines in Nigeria.