At present, the main vaccines commonly used by children in China are influenza vaccine, live attenuated varicella vaccine, Haemophilus influenzae type b vaccine, other pneumonia vaccines (23-valent pneumococcal polysaccharide vaccine, 13-valent pneumococcal polysaccharide conjugate vaccine), influenza A+C group conjugate vaccine, influenza A+C+Y+W135 group polysaccharide vaccine, pentavalent rotavirus live attenuated vaccine, polio-polio-Hib (pentavalent) combination vaccine and enterovirus 71 inactivated vaccine (hand, foot and mouth vaccine). Parents often do not know if they should be vaccinated or what the effect of vaccination is, so the following is an introduction to the common vaccines. Live attenuated varicella vaccine (to prevent chickenpox): Chickenpox is a highly contagious disease that is spread mainly by airborne droplets, so it often breaks out in kindergartens and elementary schools. Chickenpox can cause fever and skin blisters and pustules in babies, and may also cause complications such as pneumonia and meningitis, or complicate bacterial infections, while children with low immune function, chickenpox virus infection can easily develop into progressive disseminated chickenpox, with high fever and systemic toxicity symptoms, and serious illness. The most ideal way to prevent chickenpox is to get vaccinated, once when the infant is 1 year old and once when the infant is 4 years old. Chickenpox vaccination is not only for infants and children, but also for new students in junior high school, high school and college, new soldiers, teachers and daycare workers, and people with low immune function. Recommendation: Since chickenpox is still relatively common and the price of chickenpox vaccine is moderate, children of the right age should be vaccinated. Haemophilus influenzae type B vaccine (HIB vaccine): More than 20 countries in the world have included HIB vaccine in their routine immunization programs. Haemophilus influenzae type B is mainly spread through airborne droplets, and generally speaking, babies under 5 years old, especially those aged 2 months to 2 years old, are susceptible to infection. It causes not only pediatric pneumonia, but also serious diseases such as pediatric meningitis, septicemia, myelitis, otitis media, pericarditis, etc. It is the main causative agent of serious bacterial infections in babies. Recommendation: Babies who are not in good health and prone to illness are best to be vaccinated. Influenza vaccine (to prevent influenza): Influenza virus is highly contagious and the main transmission route is airborne droplet transmission, so it also often breaks out in kindergartens and elementary schools. Children infected with influenza are prone to complications such as pneumonia, otitis media and myocarditis, etc. Children aged 6 to 35 months have weaker resistance to the influenza virus compared to older children and are more likely to be infected with influenza when there is a flu epidemic. Moreover, the influenza virus itself mutates quickly, so it is necessary to receive the latest influenza virus once a year. Influenza itself is a self-limiting disease, and children with good resistance can heal themselves. Recommendation: Vaccination for babies who are not in good health or who live in groups for a long time. Influenza vaccination can be given to babies after 6 months of age and needs to be given once a year if necessary. Pentavalent live attenuated rotavirus vaccine (to prevent rotavirus diarrhea): According to the World Health Organization, diarrheal disease is the second leading cause of death in children under 5 years of age, with about 525,000 children under 5 years of age dying from diarrheal disease each year and about 1.7 billion cases of diarrheal disease in childhood each year worldwide. Rotavirus is the most common pathogen when diarrhea occurs in infants and children under 2 years of age during the fall and winter seasons. Rotavirus is transmitted mainly through fecal-oral transmission, but may also be transmitted through the respiratory tract or through fecal-contaminated food and water. The pentavalent rotavirus vaccine is administered three times, with the first dose at 6-12 weeks, followed by the next dose every 4-10 weeks, and the third dose no later than 32 weeks of age. Recommendation: Vaccination is recommended for babies who are prone to diarrhea in autumn and have poor resistance. Other pneumonia vaccines (to prevent pneumonia, such as 13-valent pneumococcal polysaccharide conjugate vaccine and 23-valent pneumococcal polysaccharide vaccine): Since pneumonia can be caused by a variety of bacteria, viruses, and other microorganisms, the effectiveness of a single vaccine is limited, so there are three common pneumonia vaccines on the market today: 13-valent pneumonia vaccine, 23-valent pneumonia vaccine, and the HIB vaccine mentioned above, the latter of which causes pneumonia. The latter may be more common, but the first two pneumonia vaccines also pose a greater health risk. The 13-valent pneumonia vaccine targets invasive pneumococci, a bacterium that can cause not only pneumonia but also meningitis, bacteremia and septic arthritis in the bloodstream, posing a significant health risk to children. 13-valent pneumonia vaccine can be administered as early as 6 weeks of age, followed by 4-8 weeks between doses, with primary immunization at 2, 4 and 6 months of age (primary immunization must be completed within 6 months of age) and a booster immunization at 12-15 months of age. One booster dose is given at 12-15 months of age. The 23-valent pneumococcal polysaccharide vaccine is recommended for the prevention of pneumonia caused by pneumococci, and is recommended for people aged 2 years and older who are at high risk. Recommended: Vaccination for babies who are not in good health and prone to pneumonia. Enterovirus 71 inactivated vaccine (HFMD vaccine) (prevention of HFMD): HFMD is a common infectious disease caused by a variety of enteroviruses, mostly in children under 5 years old. Enteroviruses are suitable for survival in a humid and hot environment and can be widely spread through the feces, throat secretions, saliva and herpes fluid of infected persons. Most children have a good prognosis, usually recovering within 1 week without sequelae. A small number of children have rapid neurological involvement after onset, manifesting as brainstem encephalitis, encephalomyelitis, and encephalomyelitis, with a high mortality rate in children who develop circulatory failure and neurogenic pulmonary edema. The vaccine became available for use in 2016 and is intended for children ≥6 months of age, the earlier the better, with a total of two doses and an interval of 28 days between doses, and it is encouraged to complete the vaccination process before 12 months of age to provide early protection. Because there is more than one manufacturer of HFMD vaccine, it is recommended to complete the vaccination program using vaccines produced by the same company. Recommendations: Vaccination for babies with poor health or those who live in groups for a long time. Other class II vaccines (e.g., influenza A+C group conjugate vaccine, influenza A+C+Y+W135 group polysaccharide vaccine, polio-polio-Hib (pentavalent) combination vaccine, inactivated hepatitis A vaccine, etc.): the common feature of these vaccines is that there is a corresponding class I vaccine, so it is perfectly possible to choose a class I vaccine for vaccination. However, the incidence of adverse reactions to these class II vaccines is smaller than that of the corresponding class I vaccines due to the manufacturing process. Moreover, some vaccines can reduce the total number of vaccinations, for example, the five doses of vaccine can be reduced from 12 doses to 4 doses, which reduces the fear and pain of children and saves parents’ valuable time. Recommendation: Families with better economic conditions can choose these second vaccines for their babies to be vaccinated. In fact, the first vaccine and the second vaccine are relative. Due to the constraints of China’s current level of economic development and vaccine supply, the second vaccine is temporarily self-funded. However, as conditions mature, class II vaccines may gradually be incorporated into the national immunization plan and thus become free class I vaccines. In fact, some vaccines such as influenza, chickenpox, pneumonia and other infectious diseases are very threatening to people, which not only cause great harm to children’s health, but also increase the economic burden of families and society. Therefore, parents can voluntarily choose to receive the second vaccine according to their own financial situation, the child’s physical condition and the doctor’s recommendation. Like Class I vaccines, Class II vaccines are only put into production after extensive experiments during the research and development stage, and are proven to be safe and effective for humans; in the production process, strict quality control measures are in place for each process; and the finished products are only marketed and sold after strict inspection and certification by the national testing department.