What is the difference between the yellow shield and the green shield in the upper right corner of the health code?

The difference lies in whether you have been vaccinated against COVID-19.

Huang Dun had a shot or two of vaccine, but he didn't get it all. Green Shield means that you have been vaccinated with COVID-19 vaccine according to regulations. Whether you are vaccinated or not can be well distinguished. In order to protect themselves and their families, everyone should be vaccinated with COVID-19 vaccine in time and establish an immune system.