Anti-vaccine activism, which collectively constitutes the "anti-vax" movement, is a set of organized activities expressing opposition to vaccination. These collaborating networks often seek to increase vaccine hesitancy by disseminating vaccine misinformation and disinformation. As a social movement, it employs tools ranging from traditional news media to various forms of online communication. Activists have primarily—though not exclusively—focused on opposing childhood vaccination, and have sought to expand their influence from niche subgroups into national political debates.
Ideas that later coalesced into anti-vaccine activism predate vaccines themselves. The movement, along with fringe doctors, has propagated various myths and conspiracy theories, alongside misinformation and disinformation. These efforts have significantly increased vaccine hesitancy and influenced public policy regarding the ethical, legal, and medical aspects of vaccination. In contrast, there is no substantive debate or hesitancy within mainstream medical circles about the benefits of vaccination; the scientific consensus is "clear and unambiguous" in favor of vaccines. Despite this consensus, the anti-vaccine movement has been partially successful in distorting the public understanding of science in popular culture.
