By Ryan StewartFor The OklahomanEvery year, the World Health Organization lists its top threats to global health. Alongside usual suspects like air pollution, cancer and heart disease, a newcomer has joined the 2019 edition: vaccine hesitancy. Vaccine hesitancy refers to delay in acceptance or refusal of vaccines despite availability of vaccination services, according to WHO. The anti-vaccine movement has gained momentum in recent years as parents refuse to vaccinate their children out of fear for autism and other side effects. A 2010 study commissioned by the Association of State and Territorial Health Officials examined parents who refuse vaccines and reasons for their refusal.Read more on NewsOK.com