Abstract
BackgroundIn 2004, universal childhood varicella vaccination was introduced in Germany. We aimed to determine the age-specific prevalence of anti-varicella zoster virus (VZV) IgG-antibodies among children in the pre-varicella vaccine era in Germany, to identify factors associated with VZV seropositivity, and to assess the suitability of a commercially available ELISA for VZV seroepidemiological studies by comparing it with an in-house fluorescent antibody to membrane antigen test (FAMA) as the gold standard.MethodsSerum samples of 13,433 children and adolescents aged 1–17 years included in the population-based German Health Interview and Examination Survey for Children and Adolescents (KiGGS; conducted 2003–2006) were tested for anti-VZV IgG by ELISA. All samples with equivocal ELISA results and a random selection of ELISA-negative and -positive samples were tested by FAMA. Statistical analyses were conducted using a weighting factor adjusting the study population to the total population in Germany. Seroprevalences were calculated as percentages (%) with a 95% confidence interval (CI). Odds ratios (OR) were computed by multivariate logistic regression to determine the association between socio-demographic factors and VZV seropositivity.ResultsThe VZV seropositivity rate was 80.3% (95% CI: 79.3–81.3) in varicella-unvaccinated children and adolescents. VZV seropositivity rates differed significantly between age groups up to age 6 years, but not by gender. Of 118 retested serum samples with an equivocal ELISA result, 45.8% were FAMA-positive. The proportion of samples tested as false-negative in by ELISA varied by age group: 2.6% in children aged 1–6 and 9% in children aged 7–17 years. Multivariate analyses showed that age, having older siblings, and early daycare start were associated with seropositivity in preschoolers; migration background reduced the chance of VZV seropositivity in schoolchildren (OR: 0.65; 0.43–0.99) and adolescents (OR: 0.62; 0.4–0.97).ConclusionIn the pre-varicella vaccine era, most children in Germany contracted varicella by age six. Schoolchildren with a migration background and children without siblings have an increased risk of being VZV seronegative and should be targeted for catch-up vaccination, if they have no history of chickenpox. ELISAs are suitable for use in population-level serosurveys on VZV, but samples with equivocal ELISA results should be retested by FAMA.
Highlights
In 2004, universal childhood varicella vaccination was introduced in Germany
The objectives of this study were: (1) to representatively describe the age-specific prevalence of anti-varicella zoster virus (VZV) IgG antibodies for children and adolescents in Germany (1–17 years of age) in the pre-varicella vaccine era, (2) to identify social factors that are associated with the acquisition of anti-VZV IgG antibodies by naturally acquired varicella, and (3) to compare the commercially available standard Enzyme-linked immunosorbent assay (ELISA) versus an in-house fluorescent antibody to membrane antigen test (FAMA)
Anti-VZV IgG antibodies tested by ELISA, Age in years weighted seroprevalence rate [% (95%confidence interval (CI))]
Summary
In 2004, universal childhood varicella vaccination was introduced in Germany. We aimed to determine the age-specific prevalence of anti-varicella zoster virus (VZV) IgG-antibodies among children in the pre-varicella vaccine era in Germany, to identify factors associated with VZV seropositivity, and to assess the suitability of a commercially available ELISA for VZV seroepidemiological studies by comparing it with an in-house fluorescent antibody to membrane antigen test (FAMA) as the gold standard. Varicella-zoster virus (VZV) is a ubiquitous human herpesvirus. Primary infection with VZV results in varicella (chickenpox), which mostly affects children and is regarded as a generally benign illness [1]. Varicella can lead to serious complications resulting in hospitalization or even death [2]. Immunity against varicella is considered to protect life-long. VZV becomes latent in the dorsal root ganglia; and later in life, VZV reactivation can cause herpes zoster (shingles)
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