We know that in the early stage of the vaccine, a small number of foreign vaccinations experienced a little abnormal situation, because these reasons may cause some people to wait and see the effect of the vaccine. This vaccination is not mandatory, and individuals are willing to do so. Vaccination, unwillingness can not be vaccinated, so there will be some people who have not been vaccinated with the new crown vaccine, this part may still have a source of infection.
Even if you have completed the new crown vaccine, you may not get immunity to produce antibodies. If your body does not produce antibodies, you may still be at risk of infection if you show up in public without wearing a mask.