Vaccine Data Loggers

A digital data logger (DDL) works by automatically monitoring and recording specific environmental parameters at preset time intervals through a sensor component. The sensor sends environmental readings in the form of electrical signals to a microprocessor unit. The microprocessor converts the signals into computer-readable data and stores it in the vaccine data logger’s internal memory. The data can then be downloaded or transmitted to a server or the cloud.

A data logger thermometer is designed with an integrated temperature sensor and a logging system unlike a conventional thermometer which only measures temperature. It automatically logs temperature changes at set intervals over a period of time.

To be safely distributed around the world, vaccines require a temperature-controlled supply chain, also known as the vaccine cold chain. The vaccine cold chain begins with the cold storage unit at the vaccine manufacturing plant, extends through the transfer of vaccine to the distributor and then to the clinic or healthcare provider’s office, and ends with the administration of the vaccine to the patient. The vaccine cold chain is a network of temperature-controlled storage and transport units like freezers, refrigerators, cold rooms, cold boxes, and carriers. With the help of special devices like vaccine data loggers, this cold chain keeps vaccines at just the right temperature during each step of the supply chain from manufacturing to vaccine administration. From the time they are manufactured until the moment of vaccination, vaccines must be continuously stored in a limited temperature range. Once vaccines are exposed to too high or too low temperatures, their active ingredients can degrade and they lose their potency or ability to protect against disease. Once lost, vaccine potency cannot be restored or regained. Most vaccines are stored between 2 to 8 °C—about the temperature of a common refrigerator, but some do require freezing temperatures (-50 to -15 °C) and others need ultra-cold temperatures (< -50 °C). Maintaining the vaccine cold chain requires three equally important elements: 1) Equipment: The best storage option for vaccines in most cases is a purpose-built unit or pharmaceutical-grade unit, specially designed for storing vaccines. For transporting vaccines, specialized portable coolers with proper packing with ice packs, barrier materials and temperature monitoring devices or vaccine data loggers are also needed to maintain the vaccine temperature within the prescribed acceptable range. A vaccine data logger with a calibrated sensor should be included in the transport container for hourly monitoring of the internal cooler temperature by vaccine transport personnel. This should be placed next to the vaccine and not adjacent to the cold pack. Typically, a series of digital data loggers (DDLs) are deployed throughout the vaccine cold chain as part of a more comprehensive vaccine monitoring. They can be placed inside a cold chain shipment, freezer, refrigerator, packaging bay, or installed at various warehouse zones. In vaccine logistics, several vaccine data loggers can be placed inside each shipment and storage unit where they will transmit temperature data directly to the cloud. The collected data can be viewed through a web application and can be used to generate detailed reports and insights into temperature variations. The vaccine data loggers have special alarm features (visual, audible, email, phone call, or SMS) to alert staff in case the vaccines have reached temperatures outside the recommended range or if there is any equipment malfunction. 2) Personnel: Staff involved with handling vaccines must be thoroughly trained on cold chain procedures, safe vaccine storage and transportation practices. Training is crucial since different vaccines require different conditions for storage and handling. There should be a vaccine coordinator assigned to develop vaccine cold chain procedures and ensure proper cold chain adherence during the transport, shipping, and receiving of vaccines. The vaccine coordinator is responsible for monitoring compliance with procedures to prevent and control cold chain violations. When vaccines arrive, staff must carefully inspect the container and its contents for any damage like broken or fractured glass to ensure that the cold chain has been maintained before storing. 3) Processes: Efficient and effective vaccine monitoring and vaccine management rely on adherence to recommended processes and procedures that are mandated by regulations. Facilities handling and storing vaccines must have detailed and up-to-date instructions for vaccine handling including contingency plans in case of emergencies. Written guidelines provide necessary information to protect and maintain the vaccine viability and should include standard operating procedures (SOPs), references, personnel training, staff evaluation, and procedures for proper storage and handling. A written emergency plan in case of power outages, equipment failures, or natural disasters should be available and prepared well in advance. This should be placed in a prominent location and be freely accessible to staff. The emergency plan includes the following key details:

• Names, addresses, and contact information of potential alternate vaccine storage facilities like hospitals, long-term care facilities, packing facilities, etc.
• Guidelines for appropriate storage of vaccines at alternate facilities and direction for drivers transporting vaccines to and from alternate storage facilities. Guidelines on how to properly pack vaccines for transport and the proper packing materials to be used.
• Specifications of vaccine storage units such as the type of storage unit including brand names, models, and serial numbers.
• Contact information for key personnel such as vaccine coordinators.
• Protocols during a disaster or power outage including provisions for fuel, backup generators, backup vaccine data loggers, and 24-hour access to the building and storage unit housing the vaccines.

The Centers for Disease Control and Prevention (CDC) and U.S. Department of Health & Human Services (HHS) recommend vaccine data loggers that have the following features:

• Detachable probe that is placed in buffered material to closely replicate the temperature of the vaccine, or a digitally buffered device that mimics a buffered probe. Ultra-cold temperature data loggers must also use air probes or probes designed specifically for ultra-cold temperatures. Examples of buffered material include:
  • A vial filled with liquid (glycol, ethanol, glycerin)
  • A vial filled with loose media (sand, glass beads)
  • A solid block of material (Teflon, aluminum)
• Continuous temperature monitoring and recording capabilities
• Display current temperature and minimum & maximum temperatures on an active display screen that is easily readable from the outside of the vaccine storage unit
• Alarm for out-of-range temperatures
• Be within +/- 1°F accuracy (+/- 0.5°C)
• Low battery indicator
• Memory stores at least 4,000 readings
• User-programmable logging interval or reading rate of every 30 minutes or less
• Current and valid certificate of calibration (Report of Calibration)

The National Institute of Standards and Technology (NIST) has also set a list of minimum design features and specification requirements for effective vaccine temperature monitoring using digital data loggers. Here are additional specifications based on studies done by the NIST using digital data loggers:

• External, detachable temperature probe with cable length > 1 m is preferred
• Temperature range of –20 °C to 40 °C (for refrigerated vaccine monitoring)
• 15-minute logging interval or reading rate
• Uncertainty or accuracy of ± 0.5 °C in the range of –1 °C to 15 °C and resolution of ± 0.1 °C
• Battery life of at least 6 months minimum
• Integrated Liquid Crystal Display (LCD) with minimum last measured temperature displayed in °C or °F and Hi/Lo alarm status indicator
• Alarm capabilities that are factory set, end-user adjustable with alarm activation at 2 °C (low) and 8 °C (high) for refrigerated vaccines
• Download data via standard computer ports (e.g., USB)

For VFC (Vaccines for Children) providers, a portable back-up data logger that stays on site is also required. They also need to maintain valid calibration certificates for all vaccine data loggers, including the back-up data logger.

Here is a list of temperature monitoring devices that are not recommended in vaccine monitoring:

• Infrared temperature monitoring devices
• Household mercury temperature monitoring devices
• Bi-metal stem temperature monitoring devices
• Food temperature monitoring devices
• Thermometers including alcohol or mercury thermometers (even if placed in fluid-filled bio-safe liquid vial)
• Chart recorders
• Temperature monitoring devices without a current and valid Certificate of Calibration Testing

These temperature monitoring devices are not recommended for vaccine monitoring as they can have significant limitations and cannot be used as substitutes for certified vaccine data loggers. Numerous testing have demonstrated that these devices are not reliable or accurate for assessing vaccine storage temperatures. They can be difficult to read or only provide information on the temperatures at the precise time they are read.

Each facility that handles and stores vaccines should have a digital data logger for each vaccine storage unit and each emergency transport unit. In addition, a backup data logger with a different calibration testing schedule is also needed in case the primary device malfunctions or is out for calibration testing. Facilities must also maintain the NIST traceable Certificate of Calibration and all manufacturer guidance documents. They also need to ensure a supply of extra batteries on-hand. Temperature data Vaccine data loggers should have an active temperature display that can be easily read by all staff from the outside of the vaccine storage unit without having to open the door. Even though the digital data logger is recording temperature data continuously, the temperature will need to be checked and manually recorded by office staff twice daily (once in the morning and once in the afternoon). The maximum and minimum temperatures should also be recorded in the morning for the previous 24 hours. This practice allows temperature excursions to be identified quickly so that immediate corrective action can be taken to prevent inadvertent loss of vaccine. This also provides an opportunity to visually inspect the vaccine storage unit, reorganize vaccines by date, and remove any expired vaccines. Vaccine data logger temperature data should also be downloaded twice monthly, reviewed weekly, and stored for at least 3 years. Documentation of known excursions or thermometer malfunctions should be recorded along with the temperature data and should include corrective actions taken to address the excursions. Temperature probe The external probe must be also placed in a central area of the storage unit and be placed as close to the vaccines as possible. It is important to note that glycol or liquid probes take longer to adjust to the unit temperature, so they need frequent checking until stable. The probe must be placed away from walls, ceilings, cooling vents, doors, floor and back of the vaccine storage unit. Do not suspend the data logger probe from wire shelves in the unit, by tape, or by other means attach to the inside ceiling of the unit. For providers who have pharmaceutical-grade storage units or purpose-built units designed for vaccine storage, here are the only allowable exceptions for the placement of the temperature probe:

• The vaccine storage unit has a built-in digital data logger
• There is a dedicated port for the probe that dictates the placement of the probe.

Wireless temperature monitoring Wireless temperature monitoring systems have the advantage of enabling monitoring of multiple vaccine storage units (refrigerators and freezers) from a single application in real-time. Wireless monitoring saves staff from having to manually disconnect and download temperatures on a weekly basis. However, a wireless temperature monitoring system does not relieve you from the requirement for once-daily min/max checks. Wireless temperature monitoring systems used in conjunction with vaccine data loggers must also have the following features or specific protocols and systems:

• Provide daily data on temperatures in readable and interpretable printed form upon requestRecord the time and date of assessment of twice daily temperature readings, including morning minimum and maximum temperatures. These temperature assessments must include the name/initials of the person assessing the temperatures as well as the time of assessment.
  • AM assessment includes current temperature and AM min/max (when the clinic opens)
  • PM assessment includes current temperature (30-60 minutes before leaving for the day)
• Electronic records and/or paper printouts must be maintained on file for at least three years.

Alarm systems alert staff when temperatures go out of range. Alarm notification systems should be in place in conjunction with data loggers. Alarm system limits should be set at 2.0 – 8.0 °C (36.0 – 46.0 °F) for refrigerators and a maximum of -15.0 °C (5.0 °F) for freezers. Alarm systems should also be tested at least once a month to ensure it is working correctly. The test is done by exposing the probe to temperatures that are out of range and verifying if the call out is working and the numbers are accurate for staff assigned to respond.

A certificate of traceability and calibration, also known as Report of Calibration) is a document that contains information about the data logger’s calibration, quality, and measurement accuracy. It validates the data logger's accuracy levels to a standardized reference. The digital data logger’s calibration must be traceable to the U.S. National Institute of Standards and Technology (NIST) and must be conducted by a service provider that is accredited under ISO Standard 17025. All certificates of calibration are required to contain:

• Model number, serial number, and date of calibration (report or issue date)
• Measurement results that indicates the unit passed the test and the documented uncertainty is within suitable limits (recommended uncertainty is +/- 1 °F or +/- 0.5 °C)
• A statement indicating that it meets International Organization for Standardization / International Electronic Commission (ISO/IEC) 17025 standards

All digital data loggers used for vaccine monitoring must be calibrated every one to two years from the last calibration testing date (date certificate was issued). The CDC also recommends that calibration testing be performed by International Laboratory Accreditation Cooperation (ILAC) Mutual Recognition Arrangement (MRA) accredited laboratories. Laboratories that have attained accreditation from an ILAC/MRA signatory body meet the requirements for traceability. These include:

• The American Association for Laboratory Accreditation (A2LA)
• Laboratory Accreditation Bureau (L-A-B)
• ANSI-ASQ National Accreditation Board (ACLASS)
• International Accreditation Services (IAS)
• Perry Johnson Laboratory Accreditation, Inc. (PJLA)
• National Voluntary Laboratory Accreditation Program (NVLAP)

Providers are required to have at least one portable backup vaccine data logger on hand for use if the current data logger is no longer working appropriately or needs calibration testing. The reason a backup data logger is required is to prevent or limit the loss of temperature data. Providers should maintain the backup digital data logger on-site to ensure that there will not be any unmonitored vaccine. The backup data logger is needed in the following cases:

• The primary data logger fails
• To monitor the temperature of vaccine that is moved during an emergency
• When the primary data logger is sent for recalibration

Requirements for backup vaccine data loggers include:

• Can be set up even during an emergency (i.e., power outage, weather events, natural disasters)
• Must be accessible 24 hours per day and no further than 30 minutes from the site if not physically on-site
• Probes for backup data loggers must be pre-conditioned (kept in a refrigerator or freezer) in case of emergency use
• Should be stored outside of the vaccine storage unit until needed
• Must have a current and valid certificate of calibration and the calibration expiration date for the backup data logger should be different from the one in use
• Must meet all the functional requirements like the primary data logger

The location of the backup data logger also needs to be noted in the Vaccine Management Plan as well as the Emergency Plan for your facility.