Varicella seroprevalence among Turkish medical students and the validity of disease history.

To the Editor: Varicella is the leading cause of vaccine-preventable death among children in the developed world. Adults with a definite history of chickenpox are usually immune, and 71% to 93% of adult patients without a definite history of varicella are also seropositive. A serologic test may thus be cost-effective for determining varicella zoster virus (VZV) immunity in adults with a negative history prior to immunization against varicella. On the contrary, children without a clear history of varicella have seroprevalence rates ranging from 9% to 68% depending on age and clinical history. An intermediate prevalence may sometimes be found in young adult populations, which have a greater risk than young children for developing serious complications such as pneumonia and encephalitis. Medical students have a high risk of exposure to varicella in pediatric clinics, especially in areas where varicella immunization is not routine as it is now in much of the world.