In a sense, the history of human flourishing is the history of human’s continuous struggle against diseases and natural disasters, and the main means to control infectious diseases is prevention, and vaccination is considered the most effective measure. After vaccination, some post-vaccination reactions may occur, such as fever and itching at the vaccination site, and some vaccinees may experience hard nodules, local swelling and pain at the vaccination site. Among a variety of vaccines, the diphtheria vaccine is the one that is more likely to show hard nodules during the childhood immunization work. In general, localized redness and itching are common more than 10 hours after vaccination, and the redness and swelling are usually <2.5 cm in extent, and this reaction usually subsides gradually in 24-48 hours. Only in a very small number of people its diameter is >5.0 cm, which will subside more slowly, 1-2 months or even longer. Individuals may also present with swollen lymph nodes or lymphadenitis and pain. Both of the latter two conditions require a visit to the doctor. Parents and children should not be overly stressed after a local reaction. Mild reactions generally do not require any treatment, while more severe local reactions can be treated with a cold compress on a clean towel for the child, and after 48 hours, a hot compress for 10 minutes several times a day. You can also use fresh potato slices or magnesium sulfate powder wet compresses, can have good results.