Is the Humane Party anti-vaccination (“anti-vax”)?

No. Vaccination has proven to be one of the most effective public health measures in history.

If a particular vaccine is tested in an unethical manner (e.g., tested without the informed consent of the person being tested), the HP would oppose that testing for the same reason it opposes torture/vivisection in all other contexts.  See, e.g., Humane Party Platform §10 .