No pressure in White Labs Tube

recently opened a tube of white labs calif ale yeast (wlp001) in order to dump it in a starter. I shook it, not like an animal, but shook well. There was no CO2 pressure release like the other tubes i've opened. in fact there was none at all. I know i need to wait and see if the starter builds up CO2 (bubbles) or any activity, but should i be worried that there didn't seem to be any build up from the tube??

Stranger things have happened. I'd say do your best to forget about it for 48 hours.

Definitely the first time I've seen anyone complain about NOT getting sprayed with yeast slurry when they open a vial...

the starter's starting to build pressure. i know it's better than being sprayed, but i'd rather be sprayed by good healthy yeast than have a dead/ bad batch ruin a labor of love....anyone buy that line of sh*t?