Highlights► In 2000, varicella incidence dramatically declined to 70% of the prevaccine rate. ► HZ reports significantly increased among adults aged 20–69 years from 2000 to 2001. ► Children with a prior history of varicella demonstrated HZ rates similar to adults. ► By 2002, the efficacy of the varicella vaccination had declined well below 80%. ► HZ morbidity costs have exceeded the cost savings from varicella-disease reductions.

Background: There is increasing evidence that herpes zoster (HZ) incidence rates among children and adults (aged <60 years) with a history of natural varicella are influenced primarily by the frequency of exogenous exposures, while asymptomatic endogenous reactivations help to cap the rate at approximately 550 cases/100,000 person-years when exogenous boosting becomes rare. The Antelope Valley Varicella Active Surveillance Project was funded by the Centers for Disease Control and Prevention in 1995 to monitor the effects of varicella vaccination in one of the three representative regions of the United States. The stability in the data collection and number of reporting sites under varicella surveillance from 1995–2002 and HZ surveillance during 2000–2001 and 2006–2007 contributed to the robustness of the discerned trends. Discussion: Varicella vaccination may be useful for leukemic children; however, the target population in the United States is all children. Since the varicella vaccine inoculates its recipients with live, attenuated varicella–zoster virus (VZV), clinical varicella cases have dramatically declined. Declining exogenous exposures (boosts) from children shedding natural VZV have caused waning cell-mediated immunity. Thus, the protection provided by varicella vaccination is neither lifelong nor complete. Moreover, dramatic increases in the incidence of adult shingles cases have been observed since HZ was added to the surveillance in 2000. In 2013, this topic is still debated and remains controversial in the United States. Summary: When the costs of the booster dose for varicella and the increased shingles recurrences are included, the universal varicella vaccination program is neither effective nor cost-effective.