Covid-19 vaccines: chilled, frozen or cryogenic?

Financial analysts at SVB Leerink, a bank, are latching onto preliminary data from vaccine developers to make some estimates of commercial viability, according to reports published in Fierce Pharma. While the information gives some insight into what could happen as the various vaccines progress through their clinical trials, there will be many questions to resolve for actual commercial distribution.

According to one Fierce Pharma article, the vaccines proposed by Moderna and by the Pfizer/BioNTech partnership will need subzero storage and shipping conditions, possibly as low at -70°C (roughly the lower limit for using dry ice as a source of cold). These vaccines are based on messenger-RNA (mRNA) technology—essentially a free-floating snippet of RNA that can elicit an immune response in the body. Other vaccine candidates, including those from Johnson & Johnson, Sanofi/Novavax and others, use a viral vector (adenovirus) to carry a “protein subunit” into the body; that subunit then confers the immune response. The virus-based vaccines (which is also typically the method used to deliver flu vaccine), generally speaking, are stored and shipped at 2-8°C.

It has been publicized, as well, that Cryoport, one of the leading providers of cryogenic containers and shipping services has been involved in trials of eight Covid-19 treatments (not necessarily vaccines). That company—much in the news in the past week because of a $275-million investment by Blackstone Group—works with liquid nitrogen (-170°C), but also has shipping equipment at other temperatures. (Generally speaking, the cutoff between “frozen” and “cryogenic” is at -150°C).

The SVB Leerink analysts hypothesize that Pfizer’s frozen vaccine, which would be viable for only 24 hours at room temperature, would require "intensive one-day vaccination events at such sites ... (that would) cover a fraction of the healthy population;" Pfizer disputes that its low-temperature requirement could be a limitation of vaccine delivery.

Companies throughout the biopharma cold chain—especially those working on the new cellular and genetic therapies—are accustomed to frozen or even cryogenic conditions; on the other hand, your corner pharmacy (or hospital) might not be. (Ironically, one of the constraints of conventional flu vaccine delivery is that subzero conditions destroy the vaccine’s efficacy.) Earlier in the summer, UPS noted that it was building “freezer farms”—storage facilities with ranks of cryogenic storage tanks—in preparation for eventual vaccine distribution; other freight handlers will likely do the same.

There are numerous other considerations to vaccine viability: some require repeat dosages, some not; patient response will vary; and—even though the US government has already purchased millions of dosages of some of the leading candidates—trial results might shut down some of the vaccines currently being tested.