TUESDAY, Aug. 10 (HealthDayNews) -- Like all vaccines, the one for chicken pox isn't foolproof, but a new study finds that when vaccinated children still get the disease, they are only half as contagious as unvaccinated kids. Their cases are also typically much less severe, said study author Dr. Jean F. Seward, of the U.S. Centers for Disease Control and Prevention. "In the average case, there are 200 to 400 lesions," she said, referring to the blister-like rash that occurs with the disease. "A bad case is up to 1,000 lesions. These 'breakthrough' cases get typically less than 50 lesions,...