And they all have commonalities. It depends very much on the mechanism of action of a vaccine. This is why they are trying to find vaccines that work on the parts of viruses that do not change -- the underlying basis of the virus, in other words -- rather than the parts that DO change in mutations.

They've done lots of research on the common cold virus. I don't remember which company, but there was one that was saying that their mechanism of action would go after the core that all cold viruses have, rather than the parts that are changeable.

Please note that the common cold is also a coronavirus. The company that said they were on the pathway to a vaccine for the cold is also researching to see if this would work on the COVID-19 virus.