anthropologist heidi larson studies why people do or don't place trust in vaccines. larson: there isn't just a world polarized between pro- and anti-vaccine populations. there's 80-plus percent in the middle who it's either just a social norm, it's good for our children and for our public health, others that are starting to question, and a certain amount of questioning is healthy. and then there's some that are starting to get more anxious and are vulnerable to tipping into becoming against vaccines if they don't feel like they're getting the right information or they are not being heard. narrator: gabriella makstman wants to vaccinate her two children, but she's chosen not to follow the recommended vaccine schedule. makstman: so, the plan is to be fully vaccinated as soon as possible, but we're doing one vaccine at a time. i don't know if that's the right way. i don't know where we came up with that. yeah, i don't know. narrator: yuliya patsay has a four-year-old and is expecting another child soon. she delayed vaccinating her oldest till she was three. i was concer