The covid vaccine has a mRNA fragment that triggers our immune system to that piece in a covid virus, which is how the vaccine ramps up our antibodies to attack the nasty virus. A poor analogy is chocolate chip ice cream; the chips (mRNA) are part of the ice cream, but you won't get brain freeze from eating a chip. Could the vaccine ramp up your immune system to go after other things? Shingles is from the Chicken Pox herpes virus; if you have had it then the virus is dormant in your body. It can be reactivated by stress or illness. So, it might be good to make sure your Shingles and other vaccinations are up to date. The covid vaccine doesn't prevent covid, it decreases your chance of getting it and the severity if you do. Covid mutates too quickly to completely corral it. Things that don't mutate, like measles and polio, could be erradicated if enough people were vaccinated.