Purpose To examine trends in varicella-related hospitalizations before and after the implementation of a national 2-dose varicella vaccination program in Israel.
Methods This retrospective chart review was performed at 3 tertiary care pediatric hospitals serving the population of greater Tel-Aviv. The medical records of all children aged 0-18 years who had been hospitalized between 1/1/2004-1/31/2012 with the diagnosis varicella, varicella zoster virus (VZV) NOS, varicella encephalitis, varicella pneumonitis, VZV with secondary infection, acute cerebellar ataxia due to VZV, post-viral cerebellar ataxia due to VZV and/or chickenpox were retrieved for analysis.
Results Before the vaccination program (2004-2008), the varicella-related hospitalization rate was 38.9/10,000 children, compared with 14.5/10,000 after the vaccination program (2009-2012), representing an overall reduction of 63% (P <0.05). The 1-6 year age group had the most prominent reduction (75%: 110/10,000 vs. 27/10,000). More of the immunocompromised children were among those hospitalized in 2009-2012 (18.4% vs. 9.7% of the non-immunocompromised children, P < 0.05). Only 3.9% of the children hospitalized in both study periods were vaccinated ( at least 1 dose). The most common complication was soft-tissue infection (60% of all children), with no difference between the 2 study periods. The most prevalent pathogens were Group A β-hemolytic streptococcus (53%) and Staphylococcus aureus (32%).
Conclusions Varicella vaccination dramatically decreased the varicella burden, both directly and possibly through herd immunity, leading to a major reduction in varicella-caused hospitalizations. More accurate monitoring of the epidemiologic impact of the 2-dose policy on varicella and herpes zoster calls for orderly collection of nationally representative data.
