If a 2-month-old baby has fever after vaccination, there is no need to be nervous. If the fever is within 24 hours of the vaccination number, and it is low fever, and there are no other clinical symptoms, it is usually considered to be a vaccination reaction, so just pay attention to drink more water and observe more. If the fever is high, i.e., the axillary surface temperature is >38.5℃, or accompanied by corresponding clinical symptoms, such as cough, nasal congestion and runny nose caused by respiratory tract infection, or nausea, vomiting and diarrhea caused by gastrointestinal tract infection, it is usually considered that the immunity is reduced after vaccination and secondary viral or bacterial infection may occur, and corresponding antiviral or antibiotic treatment is required. If repeated fever persists for more than 24 hours after vaccination, secondary infection should also usually be considered. You should also take your child to the pediatric emergency department of the hospital to examine the cause and treat the cause.