Today, a company called Novavax announced that it had completed a large efficacy trial of its COVID-19 vaccine, and the news was good. The vaccine is highly effective, it blocked severe disease entirely, and it appeared to work against some of the more recently evolved virus variants. The company says it can produce 150 million doses per month by the end of the year, and the vaccine is stable when stored in a normal freezer, so it could play a big part in the effort to administer vaccines outside of industrialized nations.
So far, US citizens have had the choice of RNA-based vaccines, like the offerings from Moderna and Pfizer/BioNTech, or a vaccine based on a harmless virus engineered to carry the coronavirus spike protein, as used in the Johnson & Johnson vaccine. (The AstraZeneca and Sputnik vaccines are similar to J&J’s.) Outside the US, many countries have used vaccines based on an inactivated coronavirus, although these have turned out not to be very effective.
The Novavax vaccine uses an entirely different technology. Vaccine production starts by identifying a key gene from the pathogen of interest—the SARS-CoV-2 spike protein, in this case—and inserting it into a virus that infects plant cells. Plant cells can easily be grown in culture, and they process any proteins they make in the same way that human cells do. (This processing can involve chemically linking sugars or cleaving off superfluous parts of the protein.) The activity ensures that the purified protein will be chemically identical to the spike protein found on the surface of the SARS-CoV-2 virus itself.