The spike protein and S1 stories are complex, and I have not grasped everything. However,
here is something to ponder: "As the paper itself notes, their patients were all admitted to the hospital, so they were already presenting with severe disease - but some of them had single-digit pg/mL concentrations, while others were at 50, 60, or higher. So you can have hospitalization-worthy severe coronavirus but still have quite low S1 concentrations...And this latest paper showing circulating S1 protein after vaccination? Coupled with the previous paper from the same group, it in fact provides strong evidence that such blood levels are not by themselves the cause of coronavirus symptoms and tissue damage."