A. This symptoms are not likely related to the vaccination or worming treatment, it might be something bad he ate, maybe a change of foo. It sounds like an upset belly.
withhold food for 6-8 hours then put him on boiled boneless chicken and rice every 6 hours, small portions for a couple days. If he gets better start reintroducing his food slowly.
If he doesn't get better take him to the vet and get him checked.
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