For vaccination of children with primary immunodeficiency diseases, we need to pay attention to these issues. 1. B-cell defects B-cell defects include diseases such as congenital anaplasmosis and common variant immunodeficiency. Children with these diseases cannot take live attenuated poliovirus vaccine, or sugar pills. Because antibodies play an important role in fighting poliovirus infection, children with defective antibody production can multiply the virus in the intestine after taking the live vaccine and then enter the central nervous system through the bloodstream, leading to polio. In addition, affected children should avoid contact with individuals who have just received live poliovirus vaccine because the intestine of individuals who have just received live poliovirus vaccine can exclude the virus and may cause indirect infection with the virus if improper hygiene attention is paid. It is also important to note that because children with these diseases cannot control the multiplication of the virus in the intestine, they can be potential sources of virus transmission, which could theoretically result in the spread of poliovirus in the population. children with B-cell defects can receive other types of vaccinations. 2. T-cell defects T-cell defects include simple T-cell defects and combined immune defects, such as Digeorge syndrome, T-cell receptor defects, MHC class II molecular defects, severe combined immune defects, adenosine deaminase defects, purine nucleotide phosphorylase defects, and ZAP-70 defects. Since T cells are the main immune cells against viral infections and intracellular bacterial infections, they can cause lethal infections if improperly vaccinated. Therefore, children with T-cell defects are strictly prohibited from receiving live attenuated vaccines such as BCG, poliovirus vaccine, measles-mumps-rubella virus vaccine, varicella virus vaccine, etc. Instead, only inactivated vaccines should be given. Phagocytosis defects Phagocytosis constitutes the first line of defense of the host against bacterial and mycobacterial infections, and phagocytosis defects mainly include chronic granulomatosis and leukocyte adhesion molecular defects. BCG vaccination is strictly prohibited for children with such diseases. 4. Other primary immunodeficiencies Interferon-γ and IL-12 are the main effector cytokines in host resistance to intracellular bacterial infections, so children with interferon-γ receptor defects, IL-12 and IL-12 receptor defects are strictly prohibited from BCG vaccination, otherwise they will cause disseminated infections caused by BCG vaccination. 5. Other causes of immune deficiency Children with symptoms of AIDS should usually not be vaccinated with live viruses or bacteria; inactivated vaccines are usually recommended. However, if there are no severe signs of immunosuppression, the measles-mumps-rubella vaccine may be administered. Children who test seropositive for HIV infection but have no clinical symptoms should be vaccinated according to the planned immunization schedule, except for the substitution of inactivated poliovirus vaccine for attenuated polio vaccine. Children treated with long-term immunosuppressive drugs (e.g., glucocorticoids, antineoplastic drugs, etc.) may have an abnormal response to vaccination, so for children receiving short-term immunosuppressive treatment, vaccination can be delayed until the treatment is terminated; children receiving long-term immunosuppressive treatment cannot receive live vaccines, but can receive inactivated vaccines. In addition, low immune function may also cause vaccination failure, such as children with eczematous thrombocytopenia with immunodeficiency who do not produce or produce only a small amount of specific antibodies after vaccination with polysaccharide vaccines (e.g., Bacille Calmette-Guérin, Haemophilus influenzae type B vaccine). In conclusion, if parents suspect that their child is immunocompromised, they should consult with an immunologist and be cautious about vaccination.