  Widespread uptake of COVID-19 vaccines is necessary to achieve herd immunity.
However, surveys have found concerning numbers of U.S. adults hesitant or
unwilling to be vaccinated. Online misinformation may play an important role in
vaccine hesitancy, but we lack a clear picture of the extent to which it will
impact vaccination uptake. Here, we study how vaccination rates and vaccine
hesitancy are associated with levels of online misinformation about vaccines
shared by 1.6 million Twitter users geolocated at the U.S. state and county
levels. We find a negative relationship between recent levels of misinformation
and daily vaccination rates. Consistently, negative opinions toward vaccines
are correlated with misinformation. Vaccine hesitancy is also strongly
associated with Republican vote share, but the association between vaccine
outcomes and misinformation remains significant when accounting for political
as well as demographic and socioeconomic factors. Hesitancy levels in
Democratic counties with high misinformation match those in Republican
counties. These results suggest that addressing online misinformation must be a
key component of interventions aimed to maximize the effectiveness of
vaccination campaigns.
