The components of the Pfizer-BioNTech mRNA COVID-19 vaccine do not permanently remain inside the human body after administration. Once the injected mRNA instructs local cellular machinery to temporarily produce a harmless spike protein piece to stimulate an immune response, cellular enzymes rapidly break down and degrade the fragile mRNA strand within days. Similarly, the lipid nanoparticles and other auxiliary ingredients are naturally metabolized, cleared, and excreted by normal physiological clearance pathways, leaving behind only the acquired immunological memory cells.