The emergence of COVID-19 spurred the fastest development of a vaccine in history. Yet, a large proportion of Americans remain hesitant to receive it. Our paper investigates how the social networks we inhabit might explain persistent vaccine hesitancy. We argue that the COVID-19 vaccination status of respondents' closest associates inhibits or motivates their decision to receive a COVID-19 vaccine. To test our argument, we conduct an original survey asking respondents a battery of questions about the people with whom individuals most frequently discuss vaccines and COVID-19. Our survey reports that individuals' discussion networks are polarized by vaccination status. Concurrently, there is a strong association between the social network's vaccination status and the respondent's vaccination status. This association is so robust that partisanship does not moderate the association between discussants' vaccination status and respondents' vaccination status. Together, our results imply that unvaccinated individuals remain hesitant because they face reinforcing social pressure from their closest associates. The unique timing of our survey, during an unprecedented vaccination campaign against a novel disease, offers a snapshot of how relationships may affect attitudes.