The side effect of enlarged breast nodules does not usually occur after the New Crown vaccine. Prompt examination is recommended, and exacerbation of breast disease cannot be ruled out. Breast nodules are palpable and obvious lumps, nodules, etc. in the breast, which may be accompanied by pain. Breast nodules may be caused by breast hyperplasia, breast tumor and other diseases. Usually, the New Crown vaccination does not affect the mammary glands and therefore does not cause the side effect of enlarged breast nodules. If you find that your breast nodules have become enlarged after receiving the New Crown vaccine, it may be due to a coincidence, i.e., a disease or other reason for the enlargement of the breast nodules, but you have received the New Crown vaccine at the same time. In this case, it is recommended to go to the hospital for a mammogram to determine the cause of the disease and treat it promptly.