Vaccines are, without a doubt, the greatest medical technological achievement of the 20th century. Thanks to its protection, certain human killers (such as smallpox) that were once so dreaded are now invisible to young people. However, many patients still die each year from various infectious diseases, a large percentage of which could have been prevented by inexpensive and effective vaccines. Below is a summary of several highly prevalent diseases (vaccine names), transmission routes, symptoms and complications. 1, chickenpox (chickenpox vaccine), the transmission channels are airborne and direct contact, symptoms: rash, fatigue, headache, fever; complications: blister infection, coagulation disorders, encephalitis, pneumonia. 2.Haemophilus influenzae type B (Hib), spread by airborne and direct contact, symptoms: may be asymptomatic unless the bacteria enter the bloodstream; complications: meningitis, mental retardation, boredom, pneumonia, death. 3.Hepatitis A (HepA), spread by diet and direct contact, symptoms: may be asymptomatic, fever, headache, stomach ache, loss of appetite, fatigue, weakness, vomiting, jaundice, dark urine; complications: Hepatitis A: liver failure, arthralgia, renal/pancreatic/hematologic dysfunction. 4, Hepatitis B (HepB), transmitted by exchange of body fluids, symptoms: may be asymptomatic, fever, headache, stomach pain, no appetite, fatigue, weakness, vomiting, jaundice, dark urine; complications: liver failure, liver cancer. 5, human papillomavirus (HPV), transmission through the exchange of body fluids, symptoms: may be asymptomatic, or genital warts; complications: cervical lesions, may lead to cervical cancer. 6.Influenza(Flu)，Transmission is by airborne and direct contact; Symptoms: fever, muscle pain, sore throat, cough, extreme fatigue; Complications: pneumonia. 7.Measles(MMR), spread by airborne and direct contact, symptoms: rash, fever, cough, runny nose, red eyes; complications: encephalitis, pneumonia, death. 8, meningococcus (MCV4/MPSV4), transmission is through the exchange of body fluids, symptoms: nausea, vomiting, photophobia, mental changes, chills, muscle pain; complications: hearing loss, brain damage, dark-colored rash, amputation, death. 9.Mumps(MMR), spread by airborne and direct contact, symptoms: parotid swelling, fever, headache, malaise, muscle pain; complications: meningitis, encephalitis, inflammation of testes or ovaries, hearing loss. 10.Polio(PCV), spread by airborne and direct contact, oral transmission, symptoms: may be asymptomatic or sore throat, fever, nausea, headache; complications: paralysis, death. 11.Pneumococcus(PCV)，Transmission through airborne and direct contact, Symptoms: may be asymptomatic or pneumonia; Complications: bacteremia, meningitis, death. 12.Rotavirus(RV)，Transmitted by mouth, Symptoms: diarrhea, fever, vomiting; Complications: severe diarrhea, dehydration. 13.Rubella(MMR)，Transmission through airborne and direct contact; Symptoms: (children) rash, fever, swollen lymph nodes; Complications: Infection in pregnant women may lead to miscarriage, preterm labor or birth defects. 14.Tetanus(TDaP)，transmitted through open wounds/skin blisters; symptoms: muscle tonus, difficulty swallowing, fever; complications: fractures, respiratory distress, death. 15. Herpes zoster (shingles vaccine), transmitted through open wounds/skin blisters and dormant virus in the body, symptoms: flu-like symptoms, unilateral burning pain in the skin, rash, photophobia; complications: postherpetic neuralgia, visual/auditory loss, encephalitis, skin infections. Remarks: At least 4 weeks should elapse between immunizations; children should receive HepA twice, the first time at 12-23 months of age and the second time 6-18 months after the first; if a child misses an immunization, he/she does not usually need to restart it, but can either wait until the next immunization or consult with his/her pediatrician.