Increased risk of herpes zoster in children with asthma: a population-based case-control study.

OBJECTIVE To determine the risk of herpes zoster (HZ) in children with and without asthma. STUDY DESIGN This study was designed as a population-based case-control study. We examined all children (aged <18 years) with possible HZ in Olmsted County, Minnesota, between 1996 and 2001 (n = 306; identified by International Classification of Diseases, Eighth Revision codes and predetermined criteria for HZ) to identify true cases. To determine the association between asthma and HZ, we compared the frequency of asthma among children with HZ with that among age- and sex-matched corresponding controls (1:1 matching) who resided in Olmsted County, Minnesota, during the study period. Asthma was ascertained based on predetermined criteria. A conditional logistic regression model was used to calculate ORs and 95% CIs. RESULTS We identified 277 eligible patients with HZ, 63 (23%) of whom had a history of asthma before the index date of HZ, compared with 35 of 277 (12.6%) matched controls (aOR, 2.09; 95% CI, 1.24-3.52; P = .006), adjusting for varicella vaccination and atopy status. The population-attributable risk percentage was 12%. Controlling for asthma and atopy status, varicella vaccination was associated with reduced risk of HZ (aOR, 0.44; 95% CI, 0.21-0.92; P = .028). CONCLUSION Asthma may be an unrecognized risk factor for reactivation of a non-airway-related latent infection such as HZ in children.