A second dose of vaccine is usually not recommended after a 19-day interval between the first dose of the New Crown vaccine. This is because the first dose of New Crown vaccine may not have produced sufficient antibodies at the 19-day interval, and the best immune response cannot be achieved with the second dose at this time, so a second dose of New Crown vaccine at the 19-day interval is not recommended. The interval time varies for different New Crown vaccines, and the following references can be made: 1. Two-dose New Crown vaccine: This is an inactivated vaccine, and the interval between two doses should be ≥3 weeks, which means that after the first dose, the second dose should be given at an interval of 21 days or more, and at the latest not more than 8 weeks, i.e., the vaccinator can give the second dose within a time frame of 21-56 days; 2. Three-dose New Crown vaccine: This is a recombinant sub unit vaccine, the interval between each vaccine dose should be ≥4 weeks and <8 weeks, i.e., the vaccine can be administered in 28-56 days. Vaccination with two or more doses of the neo-crown vaccine is intended to activate the body's immune system to produce specific antibodies against the neo-crown virus. The number of antibodies produced by the first dose is often not effective against the neo-coronavirus, so the vaccine needs to be given again after a certain interval to reactivate the immune system to effectively produce the corresponding antibodies. Too short or too long an interval can affect the effectiveness of antibody production and make the vaccine less effective. For those who are unable to receive the vaccination as required, contact the vaccination site in advance and consult with the vaccination officer. For those who have changed their place of residence and are worried about not being able to receive the vaccination, they can receive the vaccination at the vaccination site where they now live. All that is required is that the vaccinator bring the certificate of the first vaccination and a second-generation resident ID card or a related certificate, rather than having to receive the vaccination in advance.