Flu shots are vaccines. Flu has different prevalent strains each year, thus the need to try to predict which strain is going to be most prominent year to year. It is still a vaccine.
Yup, the Covid 19 shot IS a vaccine designed for a particular strain/mutation of corona virus... and remember, the common cold is also a corona virus, so is SARS, and MARS. The protection that it generates most likely will "wear off", just as it does if you "catch the flu", or if you "catch the common cold". No one knows how long the antibodies generated by the immune system response to it will last, just as we don't know how long the antibodies present in a previously infected Covid patient will last and be effective. It will be difficult to predict what "strains/mutations" of corona virus might show up from one year to the next. They've said that they've seen something like 23 variants of Covid 19 already. Viruses in particular can mutate very quickly. It's important to remember that this is the NORMAL way that biology works... it DOES mutate, and we ARE exposed to billions of variants of viruses and germs and diseases all the time... this is ALWAYS an ONGOING process.
Regardless of how you become exposed to these POTENTIAL "threats" to your system though, your immune system is challenged by the introduced "bug", and ramps up with antibodies against it. That's how God designed our immune system to function. However, once the wave of exposure wains, the immune system becomes more concerned about THE NEXT threat it encounters, and moves on to fight that next "invader", etc. Some illnesses you may have immunity to for life, some for a good number of years, some for only months. Doesn't matter if the exposure came by way of vaccine or actual disease.
The point is, this virus IS currently all around us all in our environment. Until it leaves our environment, we're all going to be exposed, and we'll all (generally) be building antibodies against it, regardless of the way we are exposed. What's different with a vaccine is, it's a CONTROLLED exposure, potentially with a "killed virus" (but sometimes with a live virus too).... the exposure is intended to be more minor.... so your immune system won't be overwhelmed before it is ready, and it then may have more time and ability to build antibodies BEFORE you're exposed to a "heavy, overwhelming dose" of the virus/disease (making you "sick")... so you're immune system has seen it before, and is prepared, and then can "fight it off", potentially without you even experiencing any "symptoms"... you've "exercised" your immune system to make it stronger. It's not the vaccine itself that "gives you" the antibodies.... that's the work of your immune system IN RESPONSE to the vaccine that they gave you. And THAT'S what BANJO was referring to above when he said,
"I will not be guilted into taking some vaccine just to "protect others" I'm not walking around making anybody sick......but to the contrary I tell everyone who wants to listen how to build and strengthen their immune system so if they do catch something they most likely won't die from it." If you tried to live in a "sterile" environment, and then you suddenly were exposed to something, you're immune system would have a very difficult time fighting it off, because it's not used to having to "fight" for you. Regular exposure to a broad diversity of "threats" is an important part of strengthening your immune system, and keeping you from becoming "sick".
Properly tested vaccines can be safe, can be an important part of this "strengthening" of the immune system as well, can be very effective against the specific strain of "bug" that they were developed for, and MAY even give you some immune system response against "related" or "similar" strains (like future mutations of a similar type)... that'll depend on how similar they are. These new Covid vaccines haven't been tested for much of anything for safety.... pretty much only tested to see if they will build an immune response to Covid.