Localized hard lumps after vaccination belong to the most common inoculation reaction. General inoculation of redness and swelling does not exceed 5cm, you can use a warm towel localized hot compresses or potato slices on the hardness, most of them subside within 2-3 days. If the vaccination is BCG, not only will there be hard nodules, but also abscesses. This is because the normal reaction to BCG vaccination is the appearance of a hard nodule 2-3 weeks after vaccination, followed by pus, after which the pus will break down and finally crust over, forming a permanent scar. If the needle eye where the baby was vaccinated is hard and the hardness and swelling is large, the lymph nodes in the armpit or neck on the same side are enlarged, and the baby has obvious fever, it is necessary to go to the hospital in time to avoid infection or other vaccine reactions.