title: Varicella infection is not associated with increasing prevalence of eczema: a U.S. population-based study.
abstract: BACKGROUND
  Chickenpox infection early in childhood has previously been shown to protect against the development of childhood eczema in line with the hygiene hypothesis. In 1995, the American Academy of Pediatrics recommended routine vaccination against varicella zoster virus in the United States. Subsequently, rates of chickenpox infection have dramatically decreased in childhood.
  
  
  OBJECTIVE
  We sought to understand the impact of declining rates of chickenpox infection on the prevalence of eczema.
  
  
  METHODS
  We analysed data from 207 007 children in the 1997-2013 National Health Interview Survey. One-year prevalence of eczema and 'ever had' history of chickenpox were analysed. Associations between chickenpox infection and eczema were tested using survey-weighted logistic regression. The impact of chickenpox on trends of eczema prevalence was tested using survey logistic regression and generalized linear models.
  
  
  RESULTS
  Children with a history of chickenpox compared with those without chickenpox had a lower prevalence [survey-weighted logistic regression (95% confidence interval, CI)] of eczema [8·8% (8·5-9·0%) vs. 10·6% (10·4-10·8%)]. In pooled multivariate models controlling for age, sex, race/ethnicity, household income, highest level of household education, insurance coverage, U.S. birthplace and family size, eczema was inversely associated with chickenpox [adjusted odds ratio (95% CI), 0·90 (0·86-0·94), P < 0·001]. The prevalence of eczema significantly increased over time (Tukey post-hoc test, P < 0·001 for comparisons of survey years 2001-13 vs. 1997-2000, 2008-13 vs. 2001-04 and 2008-13 vs. 2005-07). In multivariate generalized linear models, the odds of eczema was not associated with chickenpox in 2001-13 (P ≥ 0·06).
  
  
  CONCLUSIONS
  These findings suggest that lower rates of chickenpox infection secondary to widespread vaccination against varicella zoster virus are not contributing to higher rates of childhood eczema in the U.S.
authors.affiliation: Department of Dermatology, Feinberg School of Medicine at Northwestern University, Suite 1600, 676 N. St Clair St, Chicago, IL, 60611, U.S.A.
authors.forename: J C
authors.initials: JC
authors.lastname: Li
authors.affiliation: Departments of Dermatology, Preventive Medicine and Medical Social Sciences, Feinberg School of Medicine at Northwestern University, Chicago, IL, U.S.A.|Northwestern Medicine Multidisciplinary Eczema Center, Chicago, IL, U.S.A.
authors.forename: J I
authors.initials: JI
authors.lastname: Silverberg
mesh_terms: D000293:Adolescent; D002644:Chickenpox / Q000453:epidemiology* / Q000517:prevention & control; D019433:Chickenpox Vaccine; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D004485:Eczema / Q000453:epidemiology* / Q000821:virology; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D015995:Prevalence; D014481:United States / Q000453:epidemiology
chemical_list: D019433:Chickenpox Vaccine