The Rhode Island Department of Health encourages providers to confirm every varicella diagnosis by performing laboratory testing. In Rhode Island, 95% of children ages 19-35 months have received one or more doses of varicella-containing vaccine, so most cases of varicella occur in vaccinated children.
Clinical features of breakthrough varicella are often mild and atypical. It can be difficult to make a varicella diagnosis on clinical presentation alone as many other rashes can resemble varicella, including hand, foot, and mouth disease, poison ivy, allergic reaction, viral rash, or molluscum contagiosum. CDC’s photographs demonstrate several examples of varicella in vaccinated and unvaccinated children.
Molecular (PCR) testing is the most reliable method to confirm varicella infection. If you suspect varicella in a patient, please collect a swab and submit to a commercial laboratory for PCR testing. Use a polyester or Dacron tipped swab and follow the commercial laboratory's instructions for specimen collection and submission. Serologic (IgM) testing is not a reliable or efficient method for routine confirmation, especially in vaccinated persons. Laboratory testing for varicella can help avert unnecessary public health action and parental concern, as well as ensure that cases of varicella are properly identified and isolated.
The best method of protection against varicella is immunization. Two doses of varicella-containing vaccine are 98% effective at preventing varicella disease. Children should receive one dose between the ages of 12-15 months, and a second dose between the ages of 4-6 years.
All cases of varicella are reportable to Center for Acute Infectious Disease Epidemiology within 4 days of diagnosis. While we encourage laboratory testing, if you have diagnosed varicella by symptoms alone, the case is still reportable. Fill out the case report form and fax to 401-222-2488. Suspected cases may also be reported at 401-222-2577.