The CDC's Advisory Committee on Immunization Practices recommended the use of the three-dose Dengvaxia vaccine by Sanofi in Puerto Rico and some offshore protectorates and territories where dengue is endemic, although there is concern about children eligible for the vaccine returning to receive all three doses, which will be administered at six-month intervals. Children between the ages of 9 and 16 can be given Dengvaxia after laboratory confirmation that they have had one or more previous dengue infections.