ordinary childhood immunizations — with potentially lethal consequences." Geographical distribution Vaccine hesitancy is becoming an increasing concern, particularly in industrialized nations. For example, one study surveying parents in Europe found that 12–28% of surveyed parents expressed doubts about vaccinating their children. Several studies have assessed socioeconomic and cultural factors associated with vaccine hesitancy. Both high and low socioeconomic status as well as high and low education levels have all been associated with vaccine hesitancy in different populations. Other studies examining various populations around the world in different countries found that both high and low socioeconomic status are associated with vaccine hesitancy. An Australian study that examined the factors associated with vaccine attitudes and uptake separately found that under-vaccination correlated with lower socioeconomic status but not with negative attitudes towards vaccines. The researchers suggested that practical barriers are more likely to explain under-vaccination among individuals with lower socioeconomic status. A 2012 Australian study found that 52% of parents had concerns about the safety of vaccines. Studies have demonstrated that children of parents who refused the pertussis vaccine, varicella vaccine, and pneumococcal vaccine are 23 times more likely to contract pertussis (whooping cough), nine times more likely to catch varicella (chickenpox), and six times more likely to be hospitalized with severe pneumonia from Streptococcus pneumoniae (pneumococcus). Policy implications Multiple major medical societies including the Infectious Diseases Society of America, the American Medical Association, and the American Academy of Pediatrics support the elimination of all nonmedical exemptions for childhood vaccines. Individual liberty Compulsory vaccination policies have been controversial as long as they have existed, with opponents of mandatory vaccinations arguing that governments should not infringe on an individual's freedom to make medical decisions for themselves or their children, while proponents of compulsory vaccination cite the well-documented public health benefits of vaccination. Others argue that, for compulsory vaccination to effectively prevent disease, there must be not only available vaccines and a population willing to immunize, but also sufficient ability to decline vaccination on grounds of personal belief. Vaccination policy involves complicated ethical issues, as unvaccinated individuals are more likely to contract and spread disease to people with weaker immune systems, such as young children and the elderly, and to other individuals in whom the vaccine has not been effective. However, mandatory vaccination policies raise ethical issues regarding parental rights and informed consent. In the United States, vaccinations are not truly compulsory, but they are