If the first and second doses are of different types of vaccine products, they cannot be mixed. If they are of the same type of vaccine product, only the vaccine manufacturers are different, then they can be mixed. It is recommended to choose the same type of vaccine product to complete the vaccination, and it is not recommended to mix different types of vaccine products. It is not recommended to mix different types of vaccine products, because different types of vaccine products have different immunization mechanisms, and mixing them may affect the protective effect of the vaccine. When the supply of vaccines of the same type and from the same manufacturer is insufficient or when it is necessary to vaccinate in a different place, vaccines from other manufacturers of the same type can be selected for vaccination, which can reduce the weakening of the protective effect of the vaccine. It is recommended that vaccinators choose the same type of vaccine from the same manufacturer for better protection and ask their healthcare professional before vaccination.