Merck & Co Inc (Whitehouse Station, NJ) recently received FDA approval for the combination vaccine ProQuad for simultaneous vaccination against measles, mumps, rubella (German measles), and varicella (chickenpox) in children 12 months to 12 years of age. The product also may be used in this patient group if a second dose of measles, mumps, and rubella vaccine is to be administered. Patients should receive a 0.5-mL single dose of ProQuad subcutaneously. At least 1 month should elapse between a dose of a measles-containing vaccine and a dose of ProQuad. If a second dose of varicella-containing vaccine is required, at least 3 months should elapse. For more information, visit www.merck.com.