Smallpox vaccine does not require catch-up vaccination. The smallpox vaccine commonly used in China is mainly the liquid cowpox vaccine, which is intended for infants and children aged 12 to 24 months. It is appropriate to be vaccinated in fall, and 1 vaccination is enough. After the cowpox virus is attenuated, it is made into liquid cowpox vaccine through special process. This vaccine is safer, more reliable and is recognized as an effective way to prevent smallpox. Smallpox is an acute infectious disease caused by smallpox virus infection, which is characterized by strong contagiousness, wide range and high mortality. It spreads mainly through the patient’s breathing, sneezing and the foam produced by coughing. As long as you have been vaccinated against smallpox, you will not be infected for the rest of your life. Smallpox has been eradicated worldwide and is extinct in our country, and there is generally no risk of infection and no need for vaccination.