A vaccine is an inactivated or attenuated virus or bacterium, not an intact virus or bacterium. A vaccine is an antigenic component of a virus or bacterium with immunogenicity extracted by relevant technology, so that it loses its ability to cause disease to a certain extent, but can stimulate the body to develop an immune response and produce certain antibodies, thereby preventing the occurrence of disease. 4. live attenuated bacterial vaccines: such as BCG vaccine, plague vaccine, anthrax vaccine, etc.; 5. genetically engineered vaccines: such as hepatitis B virus vaccine, recombinant new coronavirus vaccine, new coronavirus adenovirus vector vaccine, influenza virus subunit vaccine, etc. In addition, since vaccination is contraindicated by different types of vaccines, it is recommended to be vaccinated under the guidance of a doctor.