Regarding the SARS CoV-2 vaccines, both the two mRNA types (Pfizer and Moderna) and the two DNA types (J&J and Astra Zeneca) sneak a genetic code into a person’s body to stimulate the production of a portion of the virus known as the spike protein. Note that this process is not reproducing the whole genetic code for the virus, but only for the spike protein. The genetic vaccines use different methods to hide the inoculated spike protein’s genetic code from the immune system so it can penetrate the cell when it is inoculated into an upper arm muscle. In all cases, however, many different tissues and cells of the body become the manufacturing plants for the virus’ spike protein, which is targeted for antibody production and T cell activation by providing an antigen. Different portions of the viral portions are known as antigens. This is unlike traditional vaccines that directly introduce a weaker version of the whole virus and the body responds by making antibodies to the whole virus, including 28 proteins in SARS-CoV-2 and not just the spike protein. Notably, the body’s natural immunity produces antibodies to the whole virus and not just the spike protein which is why it is more potent, longer lasting and less susceptible to variants evading it.
Several relevant observations in this published research paper have been made to compare a vaccine mRNA induced spike protein antigen to a natural COVID-19 infection antigen.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8786601/
The quantity and duration observations are of particular note. There was an abundance of vaccine induced antibodies after 16 days post second dose and still present as late as 60 days post second dose. The naturally infected person, however, showed a much broader response that was not restricted to just the spike protein. With respect to duration, the spike protein was found in the plasma of 96% of the vaccinees at day 1-2 and in 63% at day 7 after the prime vaccine dose. In contrast, spike was only detectable in 5 of 64 infected and COVID-19-positive patients. This was likely due to more successful irradication of the virus and removal of the antigens. Nonetheless, repeated vaccinations were required to maintain antibody levels, whereas it was more persistent in those that were naturally infected and recovered from COVID-19.
The question now is whether the spike protein is toxic or not. Here is but one of many papers showing that the spike protein can cross the blood/brain barrier and cause neuronal injury. Therefore, it is toxic.
https://www.frontiersin.org/articles/10.3389/fncel.2021.777738/full
Body fluids derived from the blood stream are potential carriers of the toxic spike protein when it is found in higher concentrations. However, the issue is how stable and how high can the concentration of the spike protein can be in the circulation of vaccinated individuals is questionable. This might be a significant issue for blood donors in the future. Saliva and breast milk are two body fluids that are also potential sources of spike protein. A nursing mother might provide both spike antibodies and spike protein to her infant. However, in a US study of 31 breast-feeding women, 67% experienced side effects after dose one and 61% after dose two of the vaccine.
https://www.medrxiv.org/content/10.1101/2021.04.21.21255841v1.full.pdf
Exosomes (a small vesicle secreted from a cell) containing vaccine induced spike proteins can be found in the blood stream prior to antibody formation. This could support a hypothesis of shedding of the vaccine induced spike protein.