The basic components of vaccines include antigens, adjuvants, preservatives, stabilizers, inactivators and other active ingredients. The immune function and immunogenicity of the antigenic components of the vaccine should be maintained for a long time and have good stability. The less adverse reactions of the vaccine and its compatibility after use, the better.
Antigen is the main effective active component of vaccine, and it is the specific immunogenic substance that determines vaccine. Antigens should be able to effectively stimulate the body’s immune response, including humoral immunity or (and) cellular immunity, produce protective antibodies or sensitized lymphocytes, and finally produce protective immunity against specific antigens. Antigens with strong immunogenicity include various proteins, polysaccharides, etc., while lipids are poor. Some less immunogenic antigens can be combined with adjuvants to enhance immune responses.
Adjuvants can enhance antigen-specific immune responses, enhance antibody responses, enhance mucosal delivery of vaccines, enhance immune contact, and enhance antigen immunogenicity. The ideal adjuvant should be non-toxic, safe, and must remain stable under non-refrigerated conditions, in addition to having the exact effect of enhancing the immune response to the antigen. The most commonly used adjuvants in vaccines are aluminum adjuvants and oil adjuvants. New adjuvants include bacterial toxins, CpG sequences, liposomes, and cytokines.
3. Fungicides and Preservatives
Preservatives are used to prevent contamination by foreign microorganisms. In general, liquid vaccines are added with appropriate preservatives in order to avoid the reproduction of micro-contaminated bacteria during storage. Most inactivated vaccines use preservatives such as thimerosal, 2-phenoxyethanol, azeotrope, etc.
4. Protective or stabilizer
In order to ensure the survival of viruses or other microorganisms as antigens and maintain immunogenicity, suitable stabilizers or protective agents are often added to vaccines, such as lactose, gelatin, sorbitol, etc. commonly used in freeze-dried vaccines.
In addition to physical methods such as heating, ultraviolet irradiation, etc., chemical methods are often used to inactivate virus or bacterial antigens. Commonly used chemical inactivation reagents include acetone, phenol, formaldehyde, etc. These substances have certain toxic effects on the human body. Therefore, after inactivating the antigen, it must be removed from the vaccine in time and strictly tested to ensure the safety of the vaccine.
Vaccines also need to use inactive ingredients such as buffers and salts during preparation. The type of buffer and the content of salt can affect the potency, purity and safety of the vaccine, so there are strict quality standards.