Vaccination is one of the most important strategies to prevent infectious diseases in children. Now Taiwan government provide many free vaccines for children including BCG, hepatitis B vaccine with or without HB immunoglobin, DTPa-IPV-Hib, measles vaccine, varicella vaccine, Japanese encephalitis vaccine, influenza vaccine, etc. These vaccines have changed the epidemiology of infectious diseases tremendously in children. For example, the carrier rate of HBV was 15-20% before HBV vaccination and dropped to 0.7% after the mass HBV immunization. Children hepatocellular carcinoma also markedly decreased thereafter (from 0.52/105 to 0.13/105). Nowadays, almost no invasive Hib cases occur.

In addition to free vaccines, there are some optional (self-paid) vaccines such as conjugate pneumococcal vaccine, oral rotavirus vaccine, HAV vaccine, HPV vaccine. The mass immunization of the 7-valent pneumococcal conjugate vaccine (PCV7) in USA dramatically decrease the incidence of IPD (invasive pneumococcal diseases) in young children but serotype replacement occurred. Although we only have partial immunization of PCV in Taiwan, serotype replacement (especially 19A) still occurred and remains a big threat to children now. New PCV13 can cover serotype 19A but continuos monitoring of the serotypes is necessary to detect the change of epidemiology.

Some adverse effect may occur after vaccination. For example, about 10% of infants immunized with DTPa-IPV-Hib will have fever within 24-48 hours. Some caution and warning of the possible adverse effects should be given before any vaccination.