Vaccine hesitancy, where people are reluctant or refuse to have themselves or their children vaccinated, is a growing trend among those fearing negative health outcomes from immunizations, such as the (non-existent) risk of autism. This collective uncertainty has now gathered such momentum that the World health Organization (WHO) sees fit to list vaccine hesitancy as one of its 10 threats to global health in 2019, alongside other more established dangers such as air pollution and drug-resistant bacteria.

While general immunization rates are high, the number of young children not receiving some or all of their recommended vaccines is on the rise. Health data from the Centers for Disease Control and Prevention charts a concerning uptick since 2000. According to its analysis, 1.3 percent of the children born in 2015 in the US went without any recommended vaccinations, up from 0.9 percent in 2011 and 0.3 percent in 2001.

The reasons for this are varied, but according to its vaccines advisory group, WHO lists complacency, inconvenience in accessing vaccines and a lack of confidence as driving factors in vaccine hesitancy. One survey carried out by the University of South Australia involving 604 pregnant women found a lack of trust in institutions and government to be a major factor, along with a parent's lack of personal experience in their child falling sick.