My son seems crankier after he gets his vaccinations. is this normal? it's seems to take a week before he is back to baseline in terms of mood

Vaccines: Unfortunately, irritability is a common side effect of vaccinations. Often a cool compress can be comforting.

Behavior after shots: It is likely normal if he returns to his usual self. The most common adverse effects are injection site reactions, fever and irritability which usually last a few days. If he is cranky routinely from shots it may be due to anxiety or perceived trauma. A calming, age appropriate approach may be beneficial to relieve some of his worry.