the first dose and a 98 percent conversion after the second dose (Gershon and Steinberg, 1989).
In 1995, the live, attenuated virus vaccine, Varivax (Merck & Co., Inc.) was licensed in the United States for use in healthy individuals greater than 12 months of age (CDC, 2007). The vaccine contains 1,350 plaque-forming units (PFUs) of Oka/Merck VZV; 25 mg of sucrose; 12.5 mg of hydrolyzed gelatin; and trace amounts of neomycin, fetal bovine serum, and residual components of MRC-5 (CDC, 2007). In 2005, Merck received licensure from the Food and Drug Administration to release the combination measles, mumps, rubella, and varicella (MMRV) vaccine ProQuad (Merck) for use among healthy children aged 12 months through 12 years (CDC, 2007). Each dose of ProQuad contains at least 3.0 log10 TCID50 of measles virus, 4.3 log10 TCID50 of mumps virus, and 3.0 log10 TCID50 of rubella virus in addition to 3.99 log10 PFUs of the attenuated varicella virus (Merck & Co., Inc., 2009).
Currently, two 0.5-mL doses of varicella vaccine are recommended for children older than 12 months, adolescents, and adults who show no evidence of prior immunity (CDC, 2007). For children aged 12 months to 12 years, the recommended minimum interval between the two doses is 3 months (CDC, 2007). For persons greater than 13 years of age, the recommended minimum interval is 4 weeks (CDC, 2007). Because of greater association with fevers and febrile seizures after MMRV vaccine as compared to the MMR and monovalent varicella vaccines as separate injections, the Advisory Committee on Immunization Practices recommends that individuals between 12 and 47 months of age receive the MMR and monovalent varicella vaccines as separate injections or MMRV for the first dose of the vaccines at the discretion of the administering physician and the parents (CDC, 2010b). The combination MMRV vaccine is preferred as a second dose for individuals aged between 12 months and 12 years, and as a first dose for individuals greater than 4 years of age when all four vaccines are needed and none are contraindicated (CDC, 2006, 2010b). Since 2005, about 90 percent of U.S. children aged 19–35 months have received at least one dose of varicella vaccine (CDC, 2010a).
This review of adverse events related to disseminated Oka VZV or vaccine-strain viral reactivation is divided into four sections. Two sections deal with initial adverse events (1) limited to the skin or (2) involving dissemination to other organs. The other two sections report cases of VZV reactivation as zoster either (1) involving dissemination limited to the skin or (2) involving dissemination to other organs. In the cases limited to the