If there is a situation where two vaccines need to be mixed, you need to consult with the staff at the vaccination center before proceeding, in order to avoid the consequences such as poor vaccination results or severe allergies in the body, such as respiratory distress due to laryngeal edema, optic nerve damage, generalized rash, and anaphylaxis. There are three cases of mixing two types of vaccines. The first is when two different vaccines are given at the same time, the second is when different products are used for the same vaccination injection, and the third is when two vaccines are mixed in the same syringe for injection, which is absolutely contraindicated. For the first case, a certain time interval is generally required, such as an interval of 28 days or more for different types of attenuated vaccines. For example, polio vaccine should be given about 1 month apart from other live attenuated vaccines before injection. However, there are cases where different types of inactivated vaccines are given at the same time, and generally need to be given at different sites. For example, when newborns receive BCG and hepatitis B vaccines, they can be given at different sites on the same day. In this case, there are usually no adverse consequences, and the appearance of transient dizziness and weakness is generally considered a normal vaccine reaction. For the second case, vaccination should be completed using the same product as much as possible. In special cases, such as when the vaccine is not available, or the vaccine recipient is vaccinated in a different place, the vaccination cannot be completed with the same manufacturer’s product, but the vaccination can be completed with the same type of vaccine from other manufacturers according to medical advice. For example, if the second dose is administered in a different location during the New Crown vaccination, or if the supply of vaccine from the same manufacturer is insufficient, the vaccination can be administered by a different manufacturer. Mild swelling and pain at the injection site and mild dizziness are normal vaccine reactions.