In 2010, the largest outbreak of whooping cough in over 50 years occurred in California.
Research published in March of this year showed that 81 percent of 2010 California whooping cough cases in people under the age of 18 occurred in those who were fully up to date on the whooping cough vaccine.
Eleven percent had received at least one shot, but not the entire recommended series, and only eight percent of those stricken were unvaccinated.
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