The public health community has gotten markedly better at distributing effective vaccines to the children who need them. But researchers are noticing an increase in mistrust of vaccines around the world, and they're concerned that unfounded suspicions could derail immunization programs essential to saving lives. Anti-vaccine groups in the U.S. and Europe have for years questioned the safety of vaccines like measles-mumps-rubella, or MMR; one highly publicized claim -- that the vaccine causes autism -- has been debunked over and over. But according to Heidi Larson, a researcher and lecturer at the London School of Hygiene and Tropical Medicine, anti-vaccine groups exist in developing countries as well and are getting better networked and organized. In a paper published online last month in The Lancet, Larson and her co-authors write that "current antivaccination groups have new levels of global reach and influence, empowered by the internet and social networking capacities allowing like minds to rapidly self-organise transnationally, whether for or against vaccines."