A case was defined as any individual with a diffuse maculo‐papulovesicular rash
onset from November 20, 2012 to March 7, 2013 who was diagnosed with
varicella by a physician or nurse. A susceptible contact was defined as an
individual who was exposed to a case of varicella and could not demonstrate
immunity toward the disease either by vaccination or previous history of disease
as documented by a licensed healthcare provider. SCHA and the school district
collaborated to identify susceptible contacts by reviewing immunity information
for students and staff in each affected classroom.