Vaccines, questions and answers

[SottoVoce]

@Samm

So I wonder why it has to be stored at -90F. That’s awfully darned cold. It requires two or three stage compressors. And just as curious, why does the Moderna vaccine not require that extreme of low temperatures?

Back in the 80s, I operated a guarded hot box (an apparatus used to measure heat loss of wall sections and fenestration) that was capable of temperatures down to -55F. The refrigeration unit was very expensive, fairly complicated to run, and took over an hour to achieve -50F in about 120 cubic feet of space. I’m sure cold technology has improved since then, but still, those type of freezers have got to be expensive and, I expect, temperamental.

Here’s an article about that. Seems it has to do with the lipids that are used.

Because the specific formulations are secret, Liu says, it’s not clear exactly why these two mRNA vaccines have different temperature requirements.

“It just comes down to what their data is,” she says of Moderna’s vaccine. “If their data shows that it’s more stable at a certain temperature, that’s it.”

Moderna spokesperson Colleen Hussey explained to NPR in an email that its vaccine doesn’t need to be kept so cold because of its particular “lipid nanoparticle properties and structure,” and because the company has learned from experience — it’s developed ten mRNA vaccine candidates already. “Now we don’t need [ultra-cold conditions] as the quality of product has improved and [it] doesn’t need to be highly frozen to avoid mRNA degradation,” Hussey explained.

Why Does Pfizer's COVID-19 Vaccine Need To Be Kept Colder Than Antarctica?