n Rule #1: There must be at least 4 wks. between dose #1 and dose #2. n Rule #2: There must be at least 8 wks. between dose #2 and dose #3. n Rule #3: There must be at least 4 mos. between dose #1 and dose #3. n Rule #4: No matter how delayed dose #2 or #3 is, do not start the series over again. n Suggested spacing options: 0, 1-2, 4-6 mos.; 0, 2, 12 mos.; 0, 12, 24 mos.