Many vaccinators feel that the second injection is more painful than the first one when they are vaccinated, which is mainly considered to be related to the way of vaccination, improper care, the existence of other diseases, or psychological effects, etc. 1. way of vaccination: if the angle and strength of the second injection are different from those of the first injection, it may lead to greater local tissue damage after vaccination, larger needle holes at the vaccination site, more subcutaneous bleeding, and possibly more pain and swelling. 2, improper care: improper care of the injection site after vaccination, such as bathing and swimming on the day of injection, may cause infection at the needle hole, which may also lead to more obvious pain, and bleeding and pus may occur when the infection is serious; 3, the existence of other diseases: if the vaccinator has a viral or bacterial infection before vaccination, but there are no conscious symptoms, and after vaccination, because of the lower immunity to the vaccine, the sensitivity increases, so painful symptoms appear; 4. Psychological effects: such as long queues before vaccination, long-term mental tension and anxiety may feel more obvious pain. Usually, mild pain at the vaccination site is a normal phenomenon and does not require measures to deal with it, and it can generally disappear on its own after 2-3 days. If the pain cannot be relieved for a long time, or even worsens or other uncomfortable symptoms appear, you should go to the hospital in time.