Free vaccines refer to vaccines within the national immunization program, and the specific types and times of vaccination are as follows: BCG vaccine is given at birth, and hepatitis B vaccine is given as the first dose at birth, the second dose at one month after birth, and the third dose at the sixth month after birth. Polio trivalent mixed vaccine is given at the second, third and fourth months of life. The mixed polio vaccine is given at the third, fourth, and fifth months of life, and is repeated when the baby is one and a half to two years old. The polio trivalent vaccine is repeated at the age of four. The measles vaccine is given at the eighth month of life, and the baby should receive a repeat measles vaccination at age six, as well as a repeat diphtheria mixture at age six.