Community protection against measles jeopardized
‘Herd immunity’ in 17 states threatened by low vaccination rates
![Disneyland crowd](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2015/02/030715_scistat_disneylandcrowd.jpg?fit=860%2C460&ssl=1)
PROTECTING THE HERD The measles outbreak traced to Disneyland emphasizes the importance of herd immunity: When a large fraction of a population is vaccinated against a disease, those who haven't been vaccinated experience some protection.
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