Pandemics are a global threat, with vaccination being the main weapon of control. Fear, an unpleasant emotional state caused by a threatening stimulus perception, is known to be behind inhibitory behaviours; being, with mistrust, the basis of anti-vaccine conspiracy theories (CTs). It would be appropriate to know the fear influence on these theories. In this way, a cross-sectional online survey was applied to 2.987 subjects, in a COVID-19 context, characterized by high levels of uncertainty and mistrust, with the aims of analyse the relationship between some anti-vaccine CTs and vaccination intention (VI), also the influence of fear to vaccination (VF) on TCs and VI in this context. As result, all CTs were positive predictors of VF and negative predictors of VI. The correlations were significant (p <0.001), from moderate to high, for all analysed variables, with a significant and moderate directionality and size of association. Regression analysis indicated a moderate and significant explained variance (r2 = 0.54) of CTs + VF in VI. The analysis also indicates that safety and security CTs were more strongly associated with VF (r2 = 0.347) and VI (r2 = 0.46) than other CTs. Obtained results were more significant than those found by other researchers. Knowing in each case the main anti-vaccine CTs and the associated fear can help to plan programs to increase vaccination levels.