This article in USA Today discusses the new mRNA vaccine technology underlying the Moderna and BioNTech/Pfizer vaccines with my Penn colleague Drew Weissman, who has worked on this technology for decades, and colleague Katakin Kariko, about some details of how it works and why it has the promise to bean transformative breakthrough in medicine.
This strategy has some key advantages over other vaccine strategies in that no live virus is used, it doesn’t have to be grown in eggs or existing cells (e.g. cell lines originally obtained from fetal tissue), which reduces many of the sources of side effects that other vaccines can induce as well as speeds development and production greatly.
The successful clinical application of this technology to COVID-19 could prove a watershed moment for vaccine development and medicine in general. The technology is being studies in numerous disease settings, including anemia, herpes, malaria, Zika, and even cancer and cystic fibrosis. The crisis of this pandemic has led to enormous investment and development in this new technology that may end up providing breakthroughs in other medical settings. The ability to insert targeted mRNA into cells to produce specific proteins, either to induce an antibody response (in this case) or overcome a deficiency because of a medical condition (as in anemia case), has almost limitless applications in principle that could expand the frontiers of medicine.
In the article, Weissman mentions that while this strategy produced serious inflammatory responses in animal studies in some of its earlier development, but they have figured out how to avoid them and in the current setting, these have not been observed, and in the phase 3 studies only mild side effects have been observed.
The key rub is that mRNA is very fragile, so their current solution is to encase it in fat droplets that protect it but requires cold storage. This poses some challenges for distribution but hardy insurmountabke ones. As this technology is further developed and applied to other medical contexts hopefully they will find ways to relax these requirements and enable distribution without frozen transport. Moderna already made some improvements that help make distribution a bit more feasible, and if the technology proves so useful there will be intensive efforts to further improve its viability under more mild conditions.