-Nearly every vaccine side effect in the history of vaccines occurs or starts to manifest in the first two weeks after injection. Phase 3 trials have shown that minor side effects are common (sore arm, etc) moderate effects are a possibility (fever, generalized weakness/fatigue, “flu like symptoms”) but short lived (1-2 days,) and severe reactions (anaphylaxis) is rare. While there are more moderate side effects from this vaccine compared to others, said side effects are actually signs your immune system is responding to the vaccine.
-While the Moderna vaccine and Pfizer vaccine are using a new vector (mRNA) the half life of mRNA is measured in hours (which means it will be gone from your body in days) and the protein it makes and places in your blood stream has a half life of 3-4 days (which means it too will be gone in a matter of 1-2 weeks.). Which is to say, long term side effects from the vaccine are incredibly unlikely.
-The big reason it’s on EUA is that we don’t know how long the vaccine will protect you yet, but for the foreseeable future (months) it will protect you. That’s really the hold up with full approval, not it’s safety.