After the injection of vaccination arm lumps, caused by the following reasons: First, the sterilization is not strict infection, many intramuscular injection due to local aseptic operation does not strictly lead to infection, then the injection site will form red, swelling, heat, pain and other phenomena, some patients will appear a fever, laboratory blood tests have elevated white blood cells and other circumstances, should take antibiotics anti-inflammatory drugs for treatment. Second, the individual type of vaccination drugs caused, such as children after the injection of the vaccine, often in the injection site can form a hard knot, which is a normal reaction, as long as there is no redness, swelling, heat, pain and other phenomena, is a normal vaccination reaction, can be dealt with through hot compresses and other methods, can make the hard lumps dissipate in a period of time.