Age-specific seroprevalence to varicella-zoster virus: study in Swiss children and analysis of European data

Abstract

Up to date epidemiological data provide the rationale for potential varicella immunization strategies in Europe. The scope of this study was: (1) to generate new seroprevalence data by evaluating sera of 970 individuals aged 0–16 years for the presence of IgG against Varicella-zoster virus (VZV); and (2) to review existing seroprevalence data. Of 256 individuals>12 years of age, 96.1% (95% confidence interval [CI], 93.7–98.5) were seropositive. Swiss citizens>12 years of age were less likely to be seronegative than foreign citizens (2.3 vs. 15.4%; odds ratio, 0.17; CI, 0.05–0.58). The age-specific seroprevalence curve demonstrated a peak at 7 years of age (84.9%; CI, 75.2–94.5) followed by lower rates at 8 and 9 years. A peak at 7–10 years of age was found in all previously reported seroprevalence curves (χ2-test for trend of pooled data, P=0.09; Poisson analysis, P<0.001). It is concluded that: (1)>90% of individuals in Europe acquire immunity against VZV before adolescence; (2) there is no evidence for a recent upward shift of the age at primary varicella; and (3) there may be a north-to-south gradient of seroprevalence. The peak at 7–10 years may represent a transient loss of detectable antibody by some individuals.