True, they are, but the reaction post-vax, particularly to the second dose, is an indication of a strong immune response.
per UC Davis:
”It is normal to have a stronger reaction after the second dose because that's when your immune system really kicks into gear. That big immune response is what causes the stronger reaction. It's called a boosting phenomenon, and it builds an even greater ability to defeat COVID-19. Here's how it works:
When you get the first dose, your body learns to make antibodies to fight COVID-19. Then you get the second vaccine, and you already have the antibodies ready to go, so that shot kicks them into action. That more robust immune response accounts for the stronger reactions. Those reactions tell you the vaccine is working.
Although stronger reactions after the second dose are common, experts say some people may have little or no reaction.”