mRNA Vaccine Mechanisms

Can someone explain why this the mRNA vaccine (which tells your body to produce spike protein and thus mimic the virus) produces long-lasting immunity but the actual virus which is being mimicked does not do that?

Is this similar to using MRNA to create spike protein to trigger antibody response to COVID?

The vaccine instructs cells to produce a piece of protein from the spike. There’s no such thing as “a” spike protein, the spike is a structure of proteins that enable a lot of functions for the virus. They choose a piece of protein from the structure that’s antigenic then encode the mRNA to produce that. The mRNA is delivered into the cell by the lipid transport and the cell picks up the instruction and produces the antigenic protein fragment. Your immune system responds as expected and attacks

mRNA vaccines produce antibodies targeting just the spike protein( S protein). There are other proteins on the virus like the M protein. Antibodies produced during an infection may target other parts of the virus so you can’t compare the two.

mRNA in vaccines doesn’t target anything, but encode the antigens (the spike protein in the case of SARS-CoV-2 ones) that will be used by the host immune system to synthetize the antibodies that will target precisely the same antigen present in natural viruses. These antibodies are, in a way, still being discovered by natural processes.

There are plenty of vaccines that use attenuated viruses - these also force your cells to produce antigens, and in fact the virus reproduces in your cells and damages them on its own as well. You could think of an mRNA vaccine as kind of like an attenuated virus vaccine, except for the fact that it can’t reproduce itself at all, unlike a virus.

IANACellularBiologist, but while that vaccine doesn't use mRNA (it uses a crippled version of another virus) the goal is still to get some cells calmly exposing spike proteins on its outer membrane... so I'd still group it together in the "should be easier for your body to find and dispose of the spike proteins" category.

In this case, the mRNA just gets your body to produce a part of the spike protein that is on the virus. Once the spike protein is floating around in your body, your immune system recognizes the spike protein and starts an immune response. The spike proteins themselves cannot actually replicate and attack the body. They are just a small part of the virus structure.If you inject with virus, presumably the virus would begin to replicate and attack your body.

The mRNA itself isn't doing the protection - it's training your immune system to do that for you (in a safe way).

This would require a live or weakened virus vaccine, it wouldn't be possible with mRNA-based ones.