Information has been received from a healthcare professional, author of the article, referring 82 varicella cases in School District X. All cases were mild, with a median of 14 lesions. School District X consisted of 17 schools with approximately 14,000 students. In August 2009, a 2-dose varicella vaccine school entry requirement was implemented for all students entering kindergarten and 7th grade. On May 19, 2011, health services was notified of 20 cases of varicella in three schools in School District X. The initial cases presented to healthcare providers with maculopapular rashes and were clinically diagnosed as having varicella. The majority of cases were associated with Schools A and B, elementary schools with 792 students and 718 students, respectively. The authors used the following sources to determine varicella vaccination status of students in Schools A and B: (1) computerized school vaccination records maintained by School District X and (2) parental report of the exact varicella vaccination date listed on a child's vaccination card. Report of a prior history of disease was determined from the parental survey and school health records. A case of varicella was defined as an illness with maculopapulovesicular rash without other explanation in a student in School District X with rash onset during 01-APR-2011 and 10-JUNE-2011. Students, both cases and non-cases, were categorized as 1-dose vaccinees if they had received one dose of varicella virus vaccine live (manufacturer unknown) before 01-APR-2011. Students were considered 2-dose vaccinees if they had received their second dose of varicella virus vaccine live (manufacturer unknown) before 01-APR-2011 and at least 3 months after the first dose. Cases were classified as one or two-dose vaccinees if they received their first or second dose of varicella virus vaccine live (manufacturer unknown) 42 days before illness onset respectively. Students were considered unvaccinated if they had never received varicella vaccine. Maculopapular lesion specimens from cases were tested using real-time polymerase chain reaction (PCR). A lesion specimen from the one hospitalized case-patient was tested at the hospital laboratory by PCR. Saliva specimens were collected from cases using Ora-Sure sponges (Ora-Sure Technologies) with transport media. Between 08-MAY-2011 and 02-JUN-2011, a total of 82 cases were identified among students and 1 case among staff in 8 of the 17 schools in School District X, with 60 (73%) of the cases occurring among students attending Schools A and B. All cases in School District X were in persons vaccinated with at least 1 dose except for one case in a school teacher; 45 (54.9%) were in persons vaccinated with 2 doses. Parents of 80% (48/60) of student cases at Schools A and B were interviewed. Of these 48 cases, all were classified as having mild disease (i.e., <50 lesions) with generalized lesions appearing in crops. Twenty-one out of 48 (43.8%) students were clinically diagnosed with varicella by their health-care provider; the rest were diagnosed by a school nurse. Maculopapular lesion specimens collected from 4 varicella case-patients were negative for varicella-zoster virus (VZV); specimens were collected approximately 10 days after rash onset. Additionally, 6 saliva specimens collected from 5 cases were negative for VZV DNA; specimens were collected approximately 15 days after rash onset. Fifty-eight environmental samples were collected from Schools A and B over the course of the investigation. All were negative for VZV DNA, although only 52% (30/58) of the environmental samples tested positive for B-actin, a marker for the presence of human DNA. Laboratory testing could not confirm varicella as the etiology of this outbreak, though clinical and epidemiological data suggested that at least some of the cases were caused by varicella. According to the authors, in the absence of a reliable means to rule out varicella as an etiology, outbreaks of suspected varicella will result in expenditure of time and resources by the public health sector and affected families. The authors also stated that because none of the varicella cases were laboratory confirmed, it was likely that misclassification of cases and non-cases occurred. Additional information has been requested. This is one of several reports received from the same source.