PORTLAND -- Scientists believe they may have figured out what’s behind the huge spike in whooping cough cases this year.
The United States has seen more cases in 2012 than in decades. Washington State even declared an epidemic.
Now, a new study from the Centers for Disease Control found that children with the whooping cough were less likely to have received all five doses of the vaccine.
The vaccines also lose their effectiveness over time. Five years after the final dose, they are only 75 percent effective.