'Perhaps' spike is 'shedded' aka a contagion itself. Which would make the Vaxx'd 'contagious'
Vaccines of the future could be ascontagious as viruses(2017)
https://www.popsci.com/contagious-vaccine-virus/
Scientists Developing “Contagious Vaccines” That Could Jump to Unvaccinated People
https://medium.com/this-fascinating-world/scientists-developing-contagious-vaccines-that-could-jump-to-unvaccinated-people-885f492b2ea
The controversial quest to make a 'contagious' vaccine
https://www.nationalgeographic.co.uk/science-and-technology/2022/03/the-controversial-quest-to-make-a-contagious-vaccine