Both DD and I were sent off for whooping cough tests just two weeks ago despite being immunised. You can still catch it although you're immunised and if you do, the symptoms are milder, especially the cough, than for those who aren't immunised.

Thankfully our results were clear but I'm so glad we had the tests to rule it out - didn't hurt us one bit and I wouldn't want to stuff around with WC. My friend's 4yo DD was recently diagnosed with WC after having a persistent cough which was worse in the evening. Her daughter had been immunised, said she felt fine and had even been going to school but the doctor wanted to test her to be sure and yep, it was WC.

I'd say trust you GP on this one and hope they're wrong. There is a lot of it going around (Aus wide) according to my GP.

Good luck