COVID-19 vaccines appear to be working against today’s variants, but companies are making plans to update their shots if needed. Adjusting the vaccines should be easier than coming up with the original shots. The vaccines by Pfizer and Moderna, for example, use a piece of genetic code for the spike protein on the virus that lets your immune system learn to recognize and fight the real thing. If a variant with crops up that the vaccine can’t recognize, companies would swap out that genetic code for a better match. Still, health officials would need to decide if and when to modify shots.