Clinical Survey of Natural Varicella Compared With Breakthrough Varicella After Immunization With Live Attenuated Oka/Merck Varicella Vaccine.

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A blinded clinical survey.


Four pediatric practices (two private; two hospital-based).


Healthy 12-month-old through 17-year-old children with chickenpox were studied; 92 had natural varicella and 58 had breakthrough varicella.

Measurements and results

Antibody to varicella-zoster virus was measured by the glycoprotein-based enzyme-linked immunosorbent assay. Of those with sera available, 85% were serologically confirmed. Eighty-seven percent of enrollees had a known exposure to chickenpox, with at least two thirds of each group having a greater than 4-hour or a household exposure. The numbers of total and vesicular lesions were significantly higher in the natural varicella group, regardless of exposure status (P = .021 to <.001). The group with breakthrough varicella had a significantly lower incidence of fever (P < .001) and a significantly shorter duration of illness (P < .001). Other associated constitutional complaints and complications were not significantly different between groups.


Varicella in vaccine recipients is clinically modified and significantly less severe than natural disease. Pediatrics 1993;92:833-837; varicella, modified varicella, breakthrough varicella, vaccine, immunization.

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