What are the inactivated vaccines?

Inactivated vaccine is to cultivate viruses or bacteria first, and then inactivate them with heat or chemicals (usually formalin). Inactivated vaccines can be composed of complete viruses or bacteria, or split vaccines can be composed of their split fragments. The production of split vaccine is to further purify microorganisms until the vaccine only contains the required antigen components (such as pneumococcal polysaccharide). It can be a protein vaccine or a polysaccharide vaccine. Protein vaccine includes toxoid (inactivated bacterial toxin) and subunit vaccine. Most polysaccharide vaccines consist of purified cell wall polysaccharides from bacteria; Conjugate vaccine is a vaccine obtained by chemically connecting polysaccharide with protein, thus becoming a more effective vaccine.

Inactivated vaccines often require multiple vaccinations. Inoculation 1 dose does not produce protective immunity, but only "initializes" the immune system. The second or third dose must be inoculated to produce protective immunity. The immune response it causes is usually humoral immunity with little or no cellular immunity. The titer of antibody produced by inactivated vaccine decreases with time, so it is necessary to vaccinate some inactivated vaccines regularly. Inactivated vaccines are usually not affected by circulating antibodies, and can be vaccinated even if antibodies exist in the blood (such as in infancy or after using blood products containing antibodies); It can't be replicated in vivo and can be used for people with immunodeficiency.

At present, inactivated vaccines used in China include DTP vaccine, influenza vaccine, rabies vaccine and inactivated hepatitis A vaccine.

Inactivated vaccine can make the recipient produce an immune response mainly based on humoral immunity, and the antibody produced can neutralize and remove pathogenic microorganisms and their toxins, which has a good protective effect on pathogenic microorganisms infected outside cells. Inactivated vaccines have poor or ineffective protection against viruses, intracellular parasites and parasites.