The vaccine made by Pfizer — needs to be kept extremely cold: minus 70 degrees Celsius, which is colder than winter in Antarctica. Moderna has said that its vaccine needs to be frozen too, but only at minus 20 Celsius, more like a regular freezer.
Both the Moderna and Pfizer vaccine candidates use a new approach to unlock the body’s immune defenses. The approach uses messenger RNA, or mRNA, to turn a patient’s cells into factories that make one particular coronavirus protein.
It’s a vaccine technology that’s so new, no mRNA vaccines have ever been approved by the Food and Drug Administration.
Vaccines made from mRNA can be made much faster than older vaccines could, explains Margaret Liu, a vaccine researcher who chairs the board of the International Society for Vaccines and specializes in genetic vaccines. The problem, says Liu, is that mRNA is “really easily destroyed, and that’s because there are many, many enzymes that will just break it apart.”
The first step, Liu says, was to modify the mRNA nucleosides — the “building blocks” of the RNA vaccine. “They’ve used modified versions because those are more stable,” she says.
The next step was to use lipid nanoparticles. But even with the stabilized building blocks and lipid coating, the mRNA could still fall apart easily, which is why the vaccine is frozen.
“Everything happens more slowly as you lower the temperature,” Liu says. “So your chemical reactions — the enzymes that break down RNA — are going to happen more slowly.” It’s the same idea as freezing food to keep it from spoiling.
Because the specific formulations are secret, Liu says, it’s not clear exactly why these two mRNA vaccines have different temperature requirements.
Nov. 16, 2020– Moderna, Inc. (Nasdaq: MRNA), a biotechnology company pioneering messenger RNA (mRNA) therapeutics and vaccines to create a new generation of transformative medicines for patients, today announced new data showing that mRNA-1273, its COVID-19 vaccine candidate, remains stable at 2° to 8°C (36° to 46°F), the temperature of a standard home or medical refrigerator, for 30 days. Stability testing supports this extension from an earlier estimate of 7 days. mRNA-1273 remains stable at -20° C (-4°F) for up to six months, at refrigerated conditions for up to 30 days, and at room temperature for up to 12 hours.
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