What should I show before taking the vaccine?

You need to show the certificate of exit and ID as well.
Certificate of Exit: passport, Exit-Entry Permit for Traveling to and from Hong Kong and Macao, Travel Permit for Mainlanders to Enter and Exit Taiwan (there should be valid visas or other endorsements to the passport and permits), outbound flight ticket or electronic receipt
ID: Those who are not of Chinese nationality should also show passport, certificate of employment or Registration Form of Temporary Residence for Visitors.