An operational definition is a clear, concise, detailed definition of a measure. You need operational definitions when collecting all types of data. It is particularly important when a decision is being made about whether something is defective or not defective or whether a defect exists or not.
The varicella vaccine protects against chickenpox (varicella), a common and very contagious childhood viral illness. The varicella vaccine is given by injection when kids are between 12 and 15 months old. They receive a booster shot for further protection at 4 to 6 years of age. Kids who are older than 6 but younger than 13 who have not had chickenpox also may receive the vaccine, with the two doses given at least 3 months apart. Kids 13 years or older who have not had either chickenpox or the vaccine need two vaccine doses at least 1 month apart.
There have been 2 published studies of the postexposure effectiveness of varicella vaccine. In a prospective observational study, Salzman and Garcia [ 25 ] followed 10 susceptible siblings from 7 households who were given a single dose of varicella vaccine within 3 days after household exposure to varicella (table 1).