Chickenpox seroprevalence among healthcare and social assistance workers in Catalonia (Spain)

Abstract

Chickenpox is a frequent and contagious disease in healthcare and social assistance settings, and there are limited data on seroprevalence among workers in this sector. We estimated susceptibility to chickenpox among workers, by demographic and occupational variables, and measured the rate of seroprotection after vaccination. A retrospective seroprevalence study of chickenpox (varicella) and serological vaccine response. The earliest recorded varicella serology, analyzed by the ELISA method, was identified for each worker from a health surveillance database of a group of medical and healthcare companies in Catalonia, recorded between 2004 and 2013. The total study population consisted of 2958 workers, analyzed by gender, age, birth cohort preceding and following the introduction of the vaccine in the vaccination schedule of Catalonia (born after 1993), and occupational category, regardless of exposure risk. Vaccine effectiveness was determined in a group of 59 initi lly seronegative workers by measuring ELISA-based varicella titers, obtained at least 2 months after receiving a second dose of the VARIVAX® vaccine. 2820 workers (95.3%) had protective titers (PT) to chickenpox; 507 were men (97.1%) and 2313 were women (95%). The 1993 and earlier birth cohorts had a PT of 95.4% and those born after 1993 had a PT of 80.0%. Among at-risk categories, the PT was 95.2%, whereas among those not at risk it was was 96%. By birth decade, the lowest PT was among those age 60 years or older (93.3%). The postvaccination serological response was 89.8%. The prevalence of protective varicella serologies among healthcare and social assistance workers was similar to that found in recent seroprevalence studies in the general population in Catalonia. Men have significantly higher rates of protection than women. Those born after 1993 have significantly lower rates of protective titers than those born in 1993 or earlier.