New Crown vaccines of the same composition in the same dose can be mixed, such as between two doses of inactivated New Crown vaccine; New Crown vaccines between different doses cannot be mixed, such as between two doses of New Crown vaccine and three doses of New Crown vaccine, three doses of New Crown vaccine and one dose of New Crown vaccine, or two doses of New Crown vaccine and one dose of New Crown vaccine. The one-dose New Crown vaccine all uses an adenovirus vector method that allows the immune system to collide head-on with the New Crown virus, so one dose is sufficient to achieve a sufficient antibody concentration; the two-dose New Crown vaccine all uses inactivated virus and requires two doses to allow the immune system to produce sufficient antibodies; the three-dose New Crown vaccine is a recombinant protein vaccine that is more mild in action, so three doses are required to produce sufficient antibodies. Therefore, the technology and principle of the same dose of New Crown vaccine are the same, so it can be mixed between different brands, but not between different doses. For the general public, there is no big difference between different doses of the vaccine, and all of them can produce sufficient antibodies. For elderly people who are in poor health, they can choose to get the milder two-dose or three-dose vaccine, but you cannot get two or more doses of the new crown vaccine at once. The reason why the New Crown vaccine is given in two or three doses is to increase the probability of antibody formation or antibody concentration. If two doses are given at once, it does not make the vaccination more effective, but increases the risk of adverse reactions.