Babies with fever on the second day of vaccination should generally focus on the decrease in body resistance after vaccination and secondary viral or bacterial infections, which occur within 24 hours of vaccination and generally only have low fever without other clinical symptoms and signs. If your baby has a fever on the second day, you should go to the nearest hospital and have a blood test and C-reactive protein test to understand the status of the infection. If a viral infection is considered, symptomatic support treatment should be given according to other clinical symptoms, oral antipyretics for high fever, and antiviral drugs for low fever, such as antiviral oral solution, and drinking more water as appropriate. If there is a basis for bacterial infection also need to use antibiotics, commonly used amoxicillin or cefaclor, if there is a history of penicillin, cephalosporin allergy, you can take azithromycin.