A seroprevalence survey on varicella among adults in the vaccination era in Apulia (Italy).

In 2006, the Apulia Region (Italy) introduced universal routine vaccination (URV) against varicella disease. The coverage for one dose of varicella vaccine at 24 month of age reached 91.1% in 2010 birth-cohort. Vaccination coverage for the second dose at 5-6 years was 64.8% for the cohort 2005, and 28.8% for adolescents born in 1997. The aim of the present study is to evaluate the pattern of immunity/susceptibility to varicella in Apulian adults by a seroprevalence survey carried out 6 years after the introduction of URV. The study was carried out from May 2011 to June 2012 among blood donors of the Department of Transfusion Medicine of Policlinico General Hospital in Bari. Subjects were enrolled by a convenience sample. For each enrolled patient we collected a sample of serum of 5 ml. Anti-VZV IgG in collected sera were analyzed by chemiluminescence (CLIA). We enrolled 1769 subject; 1365 (77.2%) were male with a mean age of 38.4 ± 11.7 years. 93% (95% CI=91.7-94.1) of enrolled subject presented a titre of anti-VZV IgG >164 mIU/mL. GMT of anti-VZV IgG titre was 1063.4 mIU/ml and no difference was observed between different age group. According to our data, URV did not seem to have any impact on susceptibility among adults and in particular we did not note any cluster of susceptible subjects among young adults. Also in the vaccination era, we did not note that the average age of infection shifts among adults and then we could exclude an increase of case of complicated varicella related to the URV.