He might surprise you and be okay with them. I was slightly worried leading up to my DS has his jabs as to how he'd go now that he'd "understand the whole thing" and he was fine as in super fine and it didn't bother him in the slightest. So much so that the doctor had to tell him not too look lol!. I had explained to him what was happening and that he had to get the medicine through a needle (like in Doc McStuffin) to make sure he didn't get sick and that it might hurt a little bit but not much. I also promised that we'd go shopping afterwards for a special "brave" toy. He really wasn't bothered in the slightest by them. I honoured my promise and he got his "brave" toy but to be honest I don't think they bothered him enough that he had to be brave. A few of my friends who have LOs who are month or two younger than my DS had the same reaction. No problems.

Good luck hope it goes well for you both x