Eight-month-old babies may not have any special symptoms after receiving the MMR vaccine, or they may have symptoms such as redness, swelling, pain, fever, rash and swollen lymph nodes at the vaccination site. MMR vaccine is a combination vaccine of measles, rubella and mumps vaccines, which can prevent a variety of diseases after vaccination and is a mandatory vaccination. The most common adverse reactions are redness, swelling and pain at the vaccination site, which mostly last for 2-3 days, followed by fever, which usually lasts for 1-2 days, 7-12 days after vaccination, as well as rash, enlarged lymph nodes and mumps. Localized redness, swelling, rash, lymph node enlargement, etc. generally do not need special treatment, fever, parents can follow the doctor’s advice to use ibuprofen and other drugs to reduce fever, if there is a fever, rash repeatedly or the baby obviously mental insecurity, etc. need to promptly seek medical treatment.