Much recent literature has examined the correlates of anti-vaccination beliefs, without specifying the mechanism that creates adherence to these debunked ideas. We posit that anti-vaccination beliefs are an outcome of a general psychological propensity to believe in conspiracies based on new research on the interconnectedness of conspiracy beliefs. These ideas are tested with a confirmatory factor analysis and a seemingly unrelated regression (SUR) model of a nationally representative U.S. sample from the 2016 American National Election Studies. The confirmatory factor analysis shows that anti-vaccination beliefs highly correlate with belief in the unrelated conspiracies that Obama is a Muslim and 9/11 trutherism. Our SUR models also show that all three of these very different beliefs have similar predictors. All three have a negative correlation with political trust, political knowledge, education, and a positive correlation with authoritarianism. Thus, anti-vaccination beliefs are shown to be part of a psychological propensity to believe in conspiracies.