https://www.npr.org/sections/health-shots/2021/06/06/ [login to see] /new-type-of-covid-vaccine-could-debut-soon
A new kind of COVID-19 vaccine could be available as soon as this summer.
It's what's known as a protein subunit vaccine. It works somewhat differently from the current crop of vaccines authorized for use in the U.S. but is based on a well-understood technology and doesn't require special refrigeration.
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.