Kitten vomiting after vet visit - vaccinations, stronghold or coincidence?

Hi, we picked up a new kitten this week, we already have two other cats but keeping them separate initially for slow introductions. Took him to the vet this morning around 9.30am to be checked over as I'd noticed his ears were very dirty (he's only 13wks old and never been out) and for first vaccination jab.

Vet confirmed my suspicion that he has ear mites, suggested stronghold to cover worming (preventative as no signs of worms) and the mites. Also gave us drops to use in each ear to make even more sure to treat it before any risk of passing them on to the other cats. Also gave first jab for standard things + FL.

He was fine all day, then this evening the kids came to tell me he'd been sick. Wasn't concerned at first as it was mostly food like he ate too fast. Since then he has mostly been sleeping, has got up a few times a vomited more, now just watery stuff poor thing must be running on empty :-(

He's shown no interest in food/drink since he started vomiting, after throwing up he just retreats to his bed and snoozes some more. I just wondered if it could be linked to the stronghold or the vaccination? If he's no better I will try calling the vet in the morning though being Sunday I'm not sure what the procedure is. Any advice on caring for him? he doesn't seem overly distressed, meows a bit before he's sick then seems fine straight afterwards other than a bit sleepy. Thanks

I'd be calling the vet now. Young kittens go downhill quickly and the fact that he has vomited multiple times is very concerning (especially since he isn't drinking anything.) Kitten very likely needs fluids and a dose of Cerenia to stop the vomiting.

It's possible that he is having a reaction to one of his vaccines (it sounds as if he got both the FVRCP and the Leukemia vaccine?) or the topical earmite medication.