Report of varicella outbreak in a low vaccination coverage group of otherwise healthy children in Italy: the role of breakthrough and the need of a second dose of vaccine.

We describe an outbreak of varicella at a preschool center in Southern Italy, in the period January-May 2009, among children with a vaccination coverage of 53.9% for one dose. The outbreak occurred in a small community in Puglia and enrolled 41 children. The attack rates for unvaccinated and vaccinated children were 72.3% and 12.7%, respectively. The vaccine effectiveness against disease was 82.4%. Our findings add a further piece of evidence in supporting the routine use of a second dose of vaccine for all children without a history of disease, as recently recommended by the ACIP of the CDC.
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