How did the baby hit prophylactic needle to have a fever to do

Generally speaking, vaccination is a technology that injects low-activity pathogens into the human body in different diseases to promote the body to produce antibodies. After the pathogens enter the body, the immune system will act on them, resulting in fever symptoms, which is a normal phenomenon. Generally, the temperature will not be too high, and special treatment is not required. However, if the child's temperature exceeds 38.5°C, appropriate drugs such as ibuprofen can be taken to alleviate it.