Stand-alone units that only refrigerate or only freeze are recommended by CDC. Household-style combination refrigerator/freezer units are less capable of simultaneously maintaining proper storage temperatures in both compartments. In addition, some areas of the refrigerator space may also be unusable due to uneven temperatures in the refrigerator section interior. If a household-style combination refrigerator/freezer must be used, only refrigerated vaccines should be stored in the unit: a separate stand-alone freezer should be used if the clinic also provides frozen vaccines. Pharmaceutical grade combination units designed for vaccine storage may be acceptable for use because they are engineered not to circulate air from the freezer directly into the refrigerator compartment in the way that a household-style unit does. Stand-alone units can vary in size from compact, under-the-counter (not dormitory) style to large, stand-alone, pharmaceutical grade units (which may be labeled as purpose-built for vaccine storage). For additional information see the CDC Storage and Handling Toolkit, page 9, at www.cdc.gov/vaccines/hcp/admin/storage/toolkit/storage-handling-toolkit.pdf.
One way to have confidence that the refrigerator or freezer unit you purchase will reliably maintain proper vaccine storage temperatures is to look for a unit labeled as meeting the NSF/ANSI 456 standard for vaccine storage. This voluntary certification indicates that the model has been tested and certified to maintain proper vaccine storage conditions under a range of normal clinic conditions.