Watch CBS News

Why waning herd immunity is leading to measles outbreaks

Measles were eradicated in the United States decades ago, but decreased vaccination rates have threatened the country's herd immunity against the disease. New outbreaks have been reported, including nine cases in Philadelphia that affected a hospital and a day care center. Stephen Stock reports.
View CBS News In
CBS News App Open
Chrome Safari Continue
Be the first to know
Get browser notifications for breaking news, live events, and exclusive reporting.