side effects (Adverse Effects) occur within a few weeks of the vaccine's introduction...and certainly within six months according to our board certified ID Doc...plus, solid data, after billions of does of mRNA vaccines shows clearly that getting vaccinated is an order of magnitude better than not doing so, especially wrt this concern.
Link: https://www.nationalgeographic.com/science/article/vaccines-are-highly-unlikely-to-cause-side-effects-long-after-getting-the-shot-