Distribution Methods for Pharmaceuticals, Pt. 3: Vaccines and Temperature Monitoring

In part 1 and part 2 of our series on distribution methods for pharmaceuticals, we looked at the current model of the pharmaceutical supply chain, which has evolved so significantly since the turn of the century that the federal government has passed stricter regulations, while the World Health Organization has recommended Good Distribution Practices (GDP) to ensure the safety and security of prescription medications.

In this post, we drill down to focus on vaccines. They act as a good example of how specialty medications increasingly require their own set of safety sub-guidelines – in this case, special care regarding temperature monitoring and control.

Proper vaccine storage and handling are important factors for inhibiting – and whenever possible – eradicating diseases that seriously threaten the health of global populations. Vaccines must be stored properly from the time they are manufactured until they are administered to the public. Otherwise, every time that a vaccine is exposed to an improper condition – especially a temperature excursion – potency is compromised and cannot be restored. Each year, preventable storage and handling errors result in costly revaccinations that are often too late, in addition to significant financial loss due to waste.

The Vaccine Cold Chain

The vaccine cold chain begins with the cold storage unit at the manufacturing plant, extends to transportation of the vaccine and correct storage at the provider facility, and ends with administration of the vaccine to the patient.

The Cold Chain Flowchart. Source: CDC Vaccine Storage and Handling Toolkit

Throughout the cold chain, refrigerated and frozen vaccines must maintain their optimal holding temperature. Exposure to inappropriate conditions can affect potency of any refrigerated vaccine, as a single exposure to freezing temperatures can destroy potency.

Transporting vaccines increases the potential of a temperature excursion for many reasons, including uninsulated packaging, improper coolant materials, and warm spaces within vehicles created by engine heat or solar radiation. Ambient or spot temperature monitoring will not suffice; instead, only continuous, digital monitoring occurring within shipping containers can best ensure potency.

Packing Vaccines for Distribution

Proper containers are essential for the safe shipment of vaccines. These should include at minimum:

• Portable vaccine refrigerator and freezer units with hard-sided insulation
• Coolant materials, such as frozen water bottles (NEVER dry ice)
• Insulating materials, such as bubble wrap or corrugated cardboard, enough to form two layers per container

Each transport unit should be equipped with its own temperature monitoring device (TMD), placed in areas of the unit most likely to show fluctuations. If vaccines must be transported a long distance, a refrigerated truck is recommended.

Transporting Vaccines

To ensure that vaccines arrive safely, distribution crews should be trained to follow these good distribution practices:

• Contacting the vaccine storage facility to confirm its generator is working and can accept the vaccines for storage
• Transporting diluents with their corresponding vaccines to ensure there are always equal amounts of each for reconstitution
• Taking an inventory of the vaccines and recording actions taken to protect them.

• Preventing units from being exposed to direct sunlight
• Storing vaccines at recommended temperatures immediately on arrival at the facility

Monitoring Vaccine Temperature

Storage units must maintain proper temperatures at all times to ensure potency:

• Refrigerator units: between 2° C and 8° C (36° F and 46° F)
• Freezer units: between -50° C and -15° C (-58° F and 5° F)

Continuous temperature monitoring is the only accurate method to reflect actual vaccine temperatures. A compliant TMD should be able to record:

• The time vaccines are removed from the storage unit and placed in the container
• The temperature during transport at defined intervals
• The time at the end of transport when vaccines are placed in a stable storage unit

Temperature monitoring data for each shipment should be stored for at least three years so that it can be analyzed for long-term trends. Digital storage is the best method of preserving data from loss, as well as for easy transmission to a regulatory agency.

CDC Recommends a Digital Data Logger (DDL)

The Centers for Disease Control (CDC) recommends a specific type of TMD called a “digital data logger” (DDL). A DDL provides the most accurate storage unit temperature information, including details on how long a vaccine has been exposed to a temperature excursion. Unlike a standard thermometer, which only shows the coldest and warmest temperatures reached in a unit, a DDL with a buffered probe offers the following advantages:

• Detailed information on all temperatures can be recorded at preset intervals
• A buffered probe matches vaccine temperatures more closely than standard thermometers, which tend to reflect only air temperature
• DDL software can set alarms for at the onset of temperature excursions
• Temperature data from a DDL can be stored in a cloud allowing for online retrieval at any location

CDC does not recommend the following TMDs:

• Alcohol or mercury thermometers
• Bimetal stem or infrared TMDs
• TMDs used for food
• TMDs without a current and valid Certificate of Calibration Testing

As medications become costlier and more specialized, the CDC’s guidelines for vaccine distribution are shifting towards digital solutions. In the case of vaccines, we can see how investment in a DDL is ultimately less expensive than replacing impotent vaccines wasted because of temperature excursions.

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