Never! A “dormitory-style” refrigerator is a small combination refrigerator/freezer unit that is outfitted with one exterior door and an evaporator plate (cooling coil), which is usually located inside an icemaker compartment (freezer) within the refrigerator. Dormitory-style (bar-style) units pose a significant risk of freezing vaccine even when used only for temporary storage. During testing, dormitory-style refrigerators demonstrated consistently unacceptable performance, regardless of where the vaccine was placed inside the unit. The use of dormitory-style refrigerators is specifically prohibited for storage of VFC vaccines or other vaccines purchased with public funds.
Ask the Experts: Storage & Handling
A “dormitory-style” refrigerator is a small combination refrigerator/freezer unit that is outfitted with one exterior door and an evaporator plate (cooling coil), which is usually located inside an icemaker compartment (freezer) within the refrigerator. This type of unit has severe temperature control and stability issues. However, there are compact refrigerators or freezers noted as “pharmaceutical grade” or “purpose-built for vaccine storage” that have been engineered to maintain even temperatures throughout the unit, and these may meet the needs of a small office. In general, the unit you select must be large enough to store the year’s largest vaccine inventory without crowding and to store water bottles (in a refrigerator) and frozen coolant packs (in a freezer) to minimize temperature fluctuations. One way to assure that the unit you purchase will reliably maintain proper vaccine storage temperatures is to look for a unit labeled as meeting the NSF/ANSI 456 certification standard for vaccine storage. This voluntary certification indicates that the model has been tested and certified to maintain proper storage conditions under a range of normal clinic conditions.
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.
Yes. Vaccines that are stored in the refrigerator portion of a household-style combination refrigerator/freezer should be moved away from the vent located in the refrigerator compartment. The cold air from the freezer is circulated into the refrigerator compartment to cool it, which can cause your vaccines to freeze. Inactivated vaccines must be kept between 2° and 8°C (between 36° and 46°F) and not frozen.
Generally speaking, CDC recommends avoiding the top shelf and the areas near vents due to temperature fluctuations. However, most purpose-built or pharmaceutical-grade units use a fan to circulate air within the storage area and create more uniform temperatures than household units. During a power outage, the top shelf is an area of caution for all units as the temperatures increase most quickly there. In this instance, it would be best to check with the manufacturer or owner’s manual to see if the top shelf is appropriate for storage in your unit. Units that meet the NSF/ANSI 456 voluntary certification standard are designed to deter the user from placing vaccines in areas where proper storage temperatures cannot be maintained, so any shelf available storage in a certified unit would be usable.
No. If you turn off the freezer portion of a household-style combination refrigerator/freezer, the refrigerated compartment will not maintain the proper temperature.
Vaccines should not be stored in vegetable bins nor in the space occupied by vegetable bins of a household-style refrigerator. This area is commonly closer to the motor of the unit and the temperature is different from that in the body of the refrigerator. We recommend that you remove the vegetable bins and put bottles of water in that space to help maintain a constant temperature in your refrigerator. Vaccines should be placed in the center of the refrigerator, away from the walls and floor of the unit in open containers so air can circulate around the vaccines. If using the refrigerator section of a household-style combination refrigerator/freezer unit, you do not want the top storage shelf in the refrigerator to be too close to the vent that comes from the freezer because this can expose your vaccines to freezing temperatures.
No vaccine component, including the diluent used to reconstitute a vaccine, should be stored in vegetable bins, nor in the space occupied by vegetable bins of a household-style refrigerator. CDC recommends that you position vaccines and diluents 2 to 3 inches from the unit walls, ceiling, floor, and door. If using a household-style unit, avoid storing vaccines and diluents in any part of the unit that may not provide stable temperatures or sufficient air flow, such as directly under cooling vents; in deli, fruit, or vegetable drawers; or on refrigerator door shelves. The instability of temperatures and air flow in these areas may expose vaccines to inappropriate storage temperatures. For more information, refer to page 14 of the CDC Vaccine Storage and Handling Toolkit available at www.cdc.gov/vaccines/hcp/admin/storage/toolkit/storage-handling-toolkit.pdf.
No, do not use the same unit. Frequent opening of the refrigerator door to retrieve food items can adversely affect the internal temperature of the unit and potentially damage the vaccines.
CDC recommends using separate refrigerator and freezer units for vaccine storage, but still allows use of a combination refrigerator/freezer if you only use the refrigerator portion for storing vaccines (as you are doing). CDC also recommends that you store food and beverages in a separate storage unit from vaccines, which you are technically doing, but there may still be an impact on the refrigerator temperature by the opening and closing of the freezer door by staff. (In most two-compartment units, cold air from the freezer is circulated for cooling the refrigerator.)
The best situation would be to get a stand-alone pharmaceutical/purpose-built refrigerator unit for your vaccines (consider one that meets the voluntary NSF/ANSI 456 certification for vaccine storage), and use your refrigerator/freezer combination unit for your food and drinks. For more information about storage unit features and recommendations, refer to pages 9 and 31 of the CDC Vaccine Storage and Handling Toolkit available at www.cdc.gov/vaccines/hcp/admin/storage/toolkit/storage-handling-toolkit.pdf.
CDC’s Vaccine Storage and Handling Toolkit states that if other medications and biological products must be stored in the same unit as vaccines, they must be clearly marked and stored in separate containers or bins from vaccines. Potentially contaminated items (e.g., blood, urine) should be properly contained and stored below vaccines due to risk of contamination from drips or leaks. The freezer of a household-grade unit may be used for non-vaccine, medical storage, so long as the use does not compromise the temperature range within the refrigerator compartment where vaccine is stored.
CDC recommends the use of bins, baskets, or some other type of uncovered containers that allow for organization and air circulation for vaccines and diluents within the storage unit. Storage in boxes or bins can help maintain temperature longer, especially if power is lost. Perforated bins may allow for better air circulation around the vaccine, thus helping to maintain correct temperature.
CDC does not have a specific recommendation for brands of containers or bins for storage of vaccine. We recommend that you contact your state immunization program, as they may have suggestions for purchasing this equipment. If you are a Vaccines for Children (VFC) program provider, you should contact your immunization program to ensure that you are in compliance with VFC policy.
A refrigerator or freezer that is NSF-certified for vaccine storage means the units have been tested and certified to meet the NSF/American National Standards Institute (ANSI) 456 standard. The NSF/ANSI 456 standard (or simply “NSF 456” standard) defines the criteria for construction and performance of vaccine refrigerators and freezers used in healthcare settings where vaccines are given. These criteria were developed through a collaboration with NSF, CDC, healthcare providers, public health agencies, equipment manufacturers, and vaccine manufacturers, including experts from Immunize.org.
The NSF 456 certification is a voluntary standard. CDC does not require NSF-certified units for vaccine storage in the Vaccines for Children program or any other federal program. Not all storage units capable of reliably storing vaccines have this certification; however, all storage unit models with this certification have been designed and proven to properly store vaccines under a range of normal clinic conditions. NSF-certified units would be good options for clinic staff to consider when purchasing vaccine storage units.
Every vaccine storage unit must have a temperature monitoring device (TMD). CDC recommends that vaccines be monitored using a “digital data logger” (DDL). A DDL provides the most accurate storage unit temperature information, including a detailed record of how long a unit has been operating outside the recommended temperature range (referred to as a “temperature excursion”). Unlike a simple minimum/maximum thermometer, which only shows the coldest and warmest temperatures reached in a unit, a DDL provides a log of the temperature recorded at preset intervals (at least every 30 minutes is recommended).
Many DDLs use a buffered temperature probe, which is the most accurate way to measure actual vaccine temperatures. Temperatures measured by a buffered probe match vaccine temperatures more closely than those measured by standard thermometers, which tend to reflect only air temperature. Temperature data from a DDL can either be downloaded to a computer using special software or retrieved from a website. The software or website may also allow you to set the frequency of temperature readings. Reviewing DDL data regularly is critical to ensure temperature excursions that could damage vaccines do not go on without being addressed. It is important to decide whether independent software or a website program works best for your facility.
Temperature monitoring devices that are NOT recommended include alcohol or mercury thermometers, even if placed in a fluid-filled, biosafe, liquid vial; bimetal stem devices; devices used for food; chart recorders; infrared devices; and devices that do not have a current and valid Certificate of Calibration Testing. Please note that some devices sold in hardware and appliance stores are designed to monitor temperatures for household food storage. They are not calibrated and not accurate enough to ensure vaccines are stored within the correct temperature range. Using these devices can pose a significant risk of damaging vaccines due to undetected out-of-range temperatures.
More details on temperature monitoring are available on pages 10–11 of CDC Vaccine Storage and Handling Toolkit, available at www.cdc.gov/vaccines/hcp/admin/storage/toolkit/storage-handling-toolkit.pdf. Additional details about temperature monitoring for COVID-19 and mpox vaccines are available in the addendum at the end of the toolkit.
CDC recommends that you use only a temperature monitoring device (TMD) with a Certificate of Calibration Testing (also known as a Report of Calibration). This certificate provides the TMD’s level of accuracy compared to a recognized standard. This certificate comes with the TMD when it is purchased, and it is different than the manufacturer’s warranty. While all TMDs are calibrated during manufacturing, certified calibrated TMDs undergo a second individual calibration against a reference standard from an accredited testing laboratory. Calibration testing should be done every 2 to 3 years or according to the manufacturer’s suggested timeline to ensure the accuracy of the device continues to conform to nationally accepted standards. Additional information on this topic is available on page 11 of CDC’s Vaccine Storage and Handling Toolkit, available at www.cdc.gov/vaccines/hcp/admin/storage/toolkit/storage-handling-toolkit.pdf.
A buffered temperature probe is designed to prevent misleading and rapidly fluctuating readings by protecting the TMD from sudden changes in air temperature that can occur when opening a refrigerator door. A probe is “buffered” by immersing it in a vial filled with liquid (e.g., glycol, ethanol, glycerin), loose media (e.g., sand, glass beads), or a solid block of material such as Teflon or aluminum. Vaccine packaging is more thermostable than air because the temperature of solids and fluids change more slowly than air. Standard probes that measure air temperature can fluctuate with the defrost cycles of the unit, frequent opening and closing the door on busy workdays, air circulation patterns, etc. This could lead someone to inaccurately interpret changes in air temperature to mean that the vaccine temperature was out of range.
No. CDC recommends that every vaccine storage unit must have its own TMD. An accurate temperature history that reflects actual vaccine temperatures is critical for protecting your vaccines. It is also recommended to have at least one backup TMD on site in case a primary device breaks or malfunctions.
It may take 2 to 7 days to stabilize the temperature in a newly installed or repaired refrigerator or 2 to 3 days for a freezer. Before using a unit for vaccine storage, check and record the minimum and maximum temperatures each workday for two to seven days. If temperatures cannot be recorded using a continuous digital data logger, check and record temperatures a minimum of two times each workday. Once you have two consecutive days of temperatures recorded within the recommended range, your unit is stable and ready for use. Recommended temperatures are between 2°C and 8°C (36°F and 46°F) for the refrigerator and between -50°C and -15°C (-58°F and +5°F) for the freezer.
Check and record storage unit minimum and maximum temperatures for the time since last measurement at the start of each workday. This is a requirement for VFC providers. The minimum and maximum temperatures recorded should be those obtained since the last workday when the minimum and maximum temperatures were reset. If your device does not display minimum and maximum temperatures, then check and record the current temperature a minimum of 2 times (at the start and the end of the workday). This should be done even if there is a temperature alarm at some point during the day.
If the vaccine cold chain is broken, the ambient room temperature is useful information in helping determine how to handle the compromised vaccine. Do not remove the calibrated thermometer from the refrigerator or freezer to measure the room temperature. A standard household thermometer in the room is fine for this purpose.