No kidding it’s anecdotal; I literally shared an anecdote.

I know what an immune response from a vaccine feels like. Doing both at once can definitely cause a stronger immune response than from one alone.

As someone who had a strong immune response from the covid vaccine alone, getting both at once was significantly worse.

For me it felt like I got hit by a truck on my way to the hospital for a severe flu the entire day after I got the vaccines.