In general, vaccines work by showing people's immune systems something that looks like the virus but really isn't. Consider it an advance warning; if the real virus ever turns up, the immune system is ready to try to squelch it. In the case of the coronavirus, that "something" is one of the proteins in the virus — the spike protein. The vaccines made by Johnson & Johnson, Moderna and Pfizer contain genetic instructions for the spike protein, and it's up to the cells in our bodies to make the protein itself. The first protein subunit COVID-19 vaccine to become available will likely come from the biotech company, Novavax. In contrast to the three vaccines already authorized in the U.S., it contains the spike protein itself — no need to make it, it's already made — along with an adjuvant that enhances the immune system's response, to make the vaccine even more protective.