Cold Storage Needs for COVID-19 Vaccines

As FDA reviews data on vaccines for COVID-19, healthcare providers are making plans for storage and administration of the vaccines once they become available. Some COVID-19 vaccines need to be stored at much lower temperatures than other vaccines. This may require the use of solid (frozen) carbon dioxide (CO₂), also known as dry ice. In this article, we describe the hazards associated with dry ice and recommend safe handling practices.
 

What Is Dry Ice?

Dry ice forms when gaseous CO₂ is cooled to -78.5°C (-109.3°F). It is colorless, nonflammable, and available in block, pellet, or flake form. In healthcare, it is used most often for storing and transporting biological samples, usually in a laboratory setting. Healthcare personnel involved with vaccine storage and administration do not typically handle dry ice and may not be familiar with its hazards and required safety measures.
 

Hazards of Dry Ice

CO₂ can be dangerous in both solid and gaseous form. Exposure may occur through either inhalation or contact with eyes, skin, or mouth. The hazards of dry ice can be classified as follows:

1. Contact. Due to its very cold surface temperature, dry ice can be dangerous to handle with bare hands or even with exam gloves. Direct contact either with dry ice itself or with vapors coming off it can cause severe frostbite within a short time period.

2. Asphyxiation. As dry ice warms up (e.g., when it reaches temperatures warmer than -70°C [-94°F]), it changes directly into CO₂ gas, a process known as sublimation. CO₂ gas can displace air—that is, reduce the concentration of oxygen—in a room. Breathing higher-than-normal concentrations of CO₂ can have a variety of effects: Mild to moderate increases can lead to headache and drowsiness, whereas extremely high concentrations (e.g., 80,000-100,000 parts per million) can lead to tremors, loss of consciousness, or even death.

3. Explosion. Dry ice can also sublimate into CO₂ gas if stored in a closed container (especially if the temperature in the container is not adequately controlled), which will pressurize the container. If the container is airtight, the gas will have no escape, and the container can burst, rupture, or explode, potentially leading to serious injuries.
 

Recommendations

1. Ensure that all staff that handle or work with dry ice are aware of its presence and associated hazards. Dry ice may be hard to distinguish from regular water ice or snow, so it is important to have labels and warnings to identify its presence.

2. Whenever possible, handle dry ice in large, well-ventilated areas, where its gas can escape into the atmosphere, preventing any dangerous increases in concentration.

a) If the dry ice is stored in an unventilated or minimally ventilated area, such as a cold room, cellar, walk-in refrigerator, or environmental chamber, ventilate the space before and while accessing the dry ice.

b) If transporting dry ice in a vehicle, keep windows open to bring in fresh air.

3. Use appropriate hand and eye protection when coming in contact with dry ice, to prevent frostbite.

a) Use insulated or cryogenic gloves. These can come in various lengths, with some providing coverage up to the elbow or shoulder.

b) Regular exam gloves will not provide sufficient protection.

c) Use safety eyewear such as goggles, eye shields, or face shields to protect the eyes, especially if cutting or chipping dry ice.

d) It may be useful to store any of the protective equipment near the dry ice containers to allow easy access.

e) If sharing protective equipment such as gloves, follow adequate infection control precautions. Typically, cryogenic gloves can be shared between multiple personnel, but with the current pandemic and risk of infection spread, it may be appropriate for users to wear disposable nitrile gloves (preferably a new pair) before donning shared cryogenic gloves.

4. Do not store dry ice in airtight containers such as ultralow freezers, plastic or glass bottles, or containers with screw-top lids. When possible, store it in an insulated container (e.g., special coolers designed for dry ice storage) to keep it at the desired temperature and prevent it from turning into gaseous CO₂.

5. To dispose of dry ice, place it in a well-ventilated space at room temperature. It will turn into gaseous CO₂ and disperse (within hours—the exact time will depend on the volume).

a) Do not dispose of dry ice in sinks, toilets, or drains. It can cause structural damage.

b) Do not dispose of dry ice in the trash/garbage or leave it unattended in minimally ventilated areas.