The third injection of the new crown vaccine arm hard lumps very itchy can be 24 hours after vaccination hot compresses, avoid local pressure, scratching, if accompanied by a rash, hives, etc. need to seek medical treatment with cetirizine and other drugs. After the third injection of the new crown vaccine, the local formation of hard knots, redness, swelling, pain, belong to the common adverse reactions to vaccines, mainly due to the new crown vaccine adjuvant or other excipients in the composition of the vaccine, you can use a clean towel after 24 hours of vaccination, local hot compresses, each time for 15 minutes, 3 ~ 4 times a day, generally 1 ~ 2 days can gradually improve, while avoiding local pressure, scratching, stimulation. If the injection site, especially the non-injection site or even the whole body skin rash, hives, etc. need to exclude the vaccine allergy, it is recommended to consult a doctor in a timely manner, and follow the doctor’s instructions to use cetirizine and other drugs to treat.