You may wonder when it comes to COVID-19 vaccine storage: why Moderna's longer shelf-life gives it an advantage. When it comes to pharmaceuticals, shelf-life is a critical component. A longer shelf-life means the difference between a product that is fit for consumption and one that becomes unusable too soon to be valuable. The following paragraphs give a brief background to the COVID-19 vaccine race and point out the advantages of Moderna's formula.
The COVID-19 Vaccine Race
For most residents in the US, it may appear that the pharmaceutical race for an effective vaccine against the coronavirus (COVID-19) started in Spring 2020 as the pandemic escalated. The truth is, however, that pharmaceutical companies, like Moderna and Pfizer, worked for more than a decade to develop the technology that allowed them to fast-track the current vaccines after COVID-19 hit the U.S.
Known as mRNA technology, the CDC says that the vaccines do not contain any live virus and do not carry the risk of infecting vaccinated patients. Despite its name, the mRNA vaccine never enters a person's cell nucleus nor interacts with a person's DNA.
What the new approach does is teach the body's own internal process for making proteins to trigger an immune response and thereby build the body's immunity to the virus that causes COVID-19. A vaccinated person's body creates a piece of the spike protein in COVID-19 and then breaks down and disposes of it. Once the piece of spike appears on the cell, the body's T-Cells learn to fight it off because it recognizes the protein as an infection.
Vaccine Temperature Stability: Moderna v. Pfizer
In order for drug manufacturers to be able to transport vaccines that are fit for consumption from their facilities through the distribution channels and into the hands of prescribers and health care workers, the vaccines must maintain a stable temperature. That stable temperature varies significantly from manufacturer to manufacturer.
Pfizer uses mRNA technology to produce its vaccine, too. The vaccine received FDA's emergency use approval and doctors across the US are able to vaccinate the first groups of eligible patients.
Pfizer's technology requires that the vaccine ship in dry ice at temperatures of -70 °C to +10 °C for up to 10 days unopened. Once a point-of-use facility receives Pfizer's vaccine, the facilities must store the product in one of three ways:
Ultra-low temperature freezers will keep the product fit for consumption for up to six months;
Pfizer thermal shippers can store the product for up to 30 days if the dry ice is replaced every five days; or
Hospital refrigeration units can store the product at 2-8 °C for five days.
In noteworthy contrast, Moderna's vaccine (mRNA-1273) stays stable at temperatures of 2-8°C for 30 days. This translates to 35-46 °F on the Fahrenheit scale and is the temperature of a standard home or medical refrigerator. That is six times longer than Pfizer's vaccine will stay stable in a hospital refrigeration unit. mRNA-1273 also stays stable:
at -20 °C (-4 °F) up to six months,
at refrigerator temperatures up to 30 days, and
at room temperature for up to 12 hours.
Moderna's vaccine awaits FDA approval and may start distribution before Christmas.
Shipping and Long-Term Storage
For shipping and long-term storage, Moderna anticipates that mRNA-1273 will store at -20 °C (-4 °F) for up to six months. Those temperatures are sustainable for most home and/or medical freezers whose standard temperatures range from -25° C to -15° C (-13° F to 5° F). Most pharmaceutical distribution businesses are able to both transport and store at these suggested temperatures.
Such temperatures give Moderna an advantage over Pfizer's vaccine which requires deep-freezing temperatures that are not standard for home or medical freezers. Pfizer recommends storing its COVID-19 vaccine only for short periods of time in the thermal shipping container as doing so requires:
Frequent supplies of dry ice, and
An accurate way to constantly monitor the temperature.
The Center for Disease Control (CDC) recommends changing the dry ice within 24 hours of delivery, and every five days after delivery. After the first change of dry-ice, the recipient of the product must find its own supply of dry ice. In addition, a recipient may only open the thermal shipping container that is used for storage two times a day and only for three minutes each time. The vials must store upright in the container and remain protected from any light source.
In practical terms, this means that the dry ice method is far more complicated than the mRNA-1273 shipping/long-term storage and is more susceptible to instability if directions are not followed explicitly.
Once shipments of vaccine reach destinations where health care personnel will administer the "shots", stability when stored in refrigerators is a critical concern. Moderna says that mRNA-1273 will remain stable at 2° C to 8° C (36° F to 46° F) for up to 30 days if the vaccine is still within the six months shelf-life. This is an advantage for Moderna's vaccine over its Pfizer competitor because it means that pharmacies, doctors' offices, and hospitals can easily store the vaccine vials while waiting to distribute the doses to patients.
Before dilution with saline, Pfizer's vaccine stores in the refrigerator between 2⁰C and 8⁰ C (36⁰ F to 46⁰ F) but only up to 120 hours, or five days. After the five days, staff must discard all remaining vaccine in the refrigerator. Once thawed, providers cannot refreeze Pfizer's vaccine.
Room Temperature Storage
Another important advantage of mRNA-1273 is the product's stability for a period of 12 hours at room temperature after withdrawal from cold storage in anticipation of administration to patients.
Once diluted, the Pfizer vaccine may stay at room temperature for up to six hours. That's half the amount of time that mRNA-1273 remains stable at room temperature. (Another advantage of Moderna's vaccine is that it requires no dilution.)
To learn about how the advent of COVID-19 vaccines affects cold storage companies, you may enjoy the December 2020 article from nytimes.com entitled "Wall Street Sees Cold, Hard Cash in Vaccine Storage."