There are basically two kinds of vaccines in use at the moment. The are based both on gene modification and antibodies. So back in the old days, vaccines were made with weakened viruses. These were injected into people and they would induce an immune reaction, part of which is making antibodies. The problem is that this technique was difficult and dangerous. So now they have some better techniques. The vector vaccines like Astrazeneca put a small section of the virus genetics (RNA) into another harmless virus like a chimpanzee cold virus. This carrier virus then injects the coronavirus RNA into cells which then causes the body to create an immune response. The Pfizer and Moderna use a more fancy way of delivering the corona RNA but basically it achieves the same result.

So the gene manipulation has to do with the viruses, not our genes. The part of the corona RNA that gets injected is only the part that coats for its outside shape so antibodies can be made to stop them. The bad part of the virus is of course not included in the vaccine. 

Not sure what this has to do with allergic reactions to viruses or spring rolls. An allergic reaction is when your immune system responds to something it shouldn't, like food or dog hairs or pollen. That is why you get symptoms of being sick. Your body is supposed to react to invading viruses. That is not an allergic reaction but rather a healthy immune system.