If your baby has phlegm, it is usually okay to immunize him/her if the amount is small and there are no symptoms such as fever or cough. If the baby has phlegm with symptoms such as cough and elevated temperature, it is not recommended to take vaccination. Vaccine itself is a kind of antigen, the antigen is injected into the body, so that the body produces antibodies, when the virus and bacteria invade the body, it will produce an immune response, to achieve the effect of clearing the virus and bacteria, and play a preventive effect of disease. If the baby has phlegm also accompanied by fever, sore throat, fever and other symptoms, it is not recommended to take the vaccination, at this time to take the vaccination may lead to poor immunization effect, can not play a preventive role, but also may increase the sensitivity of the child, more likely to trigger spontaneous lesions. However, if there is only phlegm, a small amount, no other discomfort, mental and dietary normal, generally can be vaccinated. Most of the vaccines will produce a slight fever after the injection. If the baby has a cough or has an elevated body temperature when the vaccine is injected, it will aggravate the symptoms of the fever, making the parents unable to differentiate whether the fever is caused by the disease or by the vaccine injection, and delaying the treatment time.