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Many dogs tend to get a little car sick. If she didn't vomit you were ahead of the game. She'll probably be much better as she gets older. Many pups have no reactions but some do have reactions to vaccinations. Common reactions are a mild fever, decreased appetite, and depression. Some dogs experience a swelling at the injection site. This should resolve itself without the need for vet care.
Severe reactions are sudden onset of diarrhea, vomiting, swelling of the face and non-responsiveness. If these signs occur you should contact your vet immediately. Your vet may recommend benadryl at up to 2mg per pound every 8 hours. You can read about this here:
At 6 weeks of age, she is going to sleep the majority of time. Puppies also twitch quite often when they sleep. It is normal behavior for puppies and not just post vaccination. You will find that pups even bark in their sleep and run as well, so don't be surprised if the pups legs take off.
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