I have been reading there are a number of different injections how do we know which one is injected into whom?
Do you mean the vaccine injections? The computer system records what shots we get.
All of the current vaxxes were built on the original Alpha spike. The mRNAs probably just clipped it using CRISPR. J&J, Astra Zeneca used different technology but still the Alpha spike as their model. That’s why the two variants with mutated Spikes, Delta and Omicron are able to elude the vaccines.
There should be some 2nd generation vaccines that target more than the Alpha spike and those should be far more effective. The 1st gen vaxxes under Warp Speed needed to be ready within one year so that forced them to be simple in design rather than robust. A weakness that Delta and Omicron got around.