Per the article
The mRNA shots cause the body to make huge amounts of spike protein. Vaccine advocates have generally argued that those proteins remain bound to the cells where they were produced.
But the researchers also said they had found spike protein in the blood following mRNA shots at levels as high as those produced by coronavirus infection itself:
At least some portion of spike antigen generated after administration of BNT162b2 becomes distributed into the blood. We detected spike antigen in 96% of vaccinees in plasma collected one to two days after the prime injection, with antigen levels reaching as high as 174 pg/mL. The range of spike antigen concentrations in the blood of vaccinees at this early time point largely overlaps with the range of spike antigen concentrations reported in plasma in a study of acute infection.
What is the problem?