RESUMO
This study assessed the seroprevalence of varicella antibodies in children and adolescents in Spain and evaluated the reliability of two methods for detecting susceptible individuals: (1) parental-reported history of varicella and (2) medically-documented histories maintained by the pediatrician. A total of 186 children (6 to 15 years of age) were recruited in 13 pediatric offices of Valencia, Spain. A brief case report form was completed including previous history of varicella referred by the parents, and a 5 mL blood sample was obtained. The pediatrician medical file was reviewed for antecedent of varicella. The overall prevalence of varicella antibodies was 84% and 88% in the 6-9 years and 10-15 years age brackets, respectively. The predictive value of a negative history of varicella disease was 48% by parental recall (52% "false negative"), and only 26% by medical record (74% "false negative"). However, the positive predictive value of a positive parental reported history or a positive medically-documented history was 95%. The most effective strategy for varicella vaccination of older children and adolescents in Spain will be to immunize those individuals with a lack of positive (unknown or negative) history of disease.