From 2000 to 2011, the proportion of religiously exempt children in New York rose from 23 in 10,000 to 45 in 10,000. In 2000, four counties had religious exemption rates of more than 1%. By 2011, 13 counties had reached this level.
A U.S. study has shown the importance of people's social networks in vaccination choices, with the presence of anti-immunization friends correlating with parents deciding against giving shots.
On the Tanzanian island of Zanzibar, some individuals may not even need a vaccine to protect them against cholera. Research shows herd immunity has helped guard against the disease in sub-Saharan Africa.
For the first time, boys in Australia will receive the Gardasil vaccine, a series of shots typically given to high school-aged girls to prevent HPV, which can lead to cervical cancer in women.