evidence: For COVID-19 vaccines, all of the approved vaccines so far used the spike protein. The spike protein is located on the outside of a coronavirus and is how SARS-CoV-2 (the coronavirus) enters human cells. Its location on the outside of the virus makes it so the immune system can recognize it easily. [...] The Infectious Disease Society of America (IDSA) estimates that the spike proteins that were generated by COVID-19 vaccines last up to a few weeks, like other proteins made by the body. The immune system quickly identifies, attacks and destroys the spike proteins because it recognizes them as not part of you. This "learning the enemy" process is how the immune system figures out how to defeat the real coronavirus. It remembers what it saw and when you are exposed to coronavirus in the future it can rapidly mount an effective immune response.