Background and objective: An outbreak of varicella is described in a training and work center for psychologically handicapped adults with a high susceptibility to the disease.
Patients and method: Descriptive and case-control study. A questionnaire self-complimented by parents and staff of the center was used. A serologic study in order to determine antibodies againts varicella was carried out for people without varicella vaccination or disease history.
Results: Four cases of varicella occurred among 56 students of the center and none among the staff (12 people). 51.8% of students had not history of varicella versus 8.3% of staff (p = 0.009). A recommendation of vaccination against varicella was made for people without history of varicella, and 52.2% were vaccinated. After vaccination, no new cases occurred. In the serological study (11 students and 1 staff), 5 students were sero-negative. In the case-control study, risk of suffering varicella was lower for students with history of varicella, those vaccinated against varicella and those attending less commonly the center.
Conclusions: The outbreak occurred in a high susceptible population, and it is suggested that it is a previously unidentified group of risk. Serological studies of varicella with vaccination of susceptible individuals in these populations may be indicated.