What are the active ingredients in vaccines?

Generally, vaccine active ingredients include inactivated viruses, attenuated live viruses, recombinant proteins, polysaccharide substances, and viral vectors. The details are as follows:

1. Inactivated virus: Viruses are treated with chemical agents (such as formaldehyde) or physical methods (such as heating) to eliminate their infectivity while preserving their antigenic structure. After vaccination, they can stimulate the body to produce antibodies and prevent corresponding viral infections. This type is commonly used in influenza vaccines and inactivated poliovirus vaccines.

2. Attenuated live virus: Through cultivation and screening, viral strains with significantly reduced toxicity are obtained. After vaccination, these viruses can replicate slightly within the body, simulating natural infection and triggering a long-lasting immune response. Varicella (chickenpox) vaccines and measles-mumps-rubella (MMR) combination vaccines often use this type of active ingredient.

3. Recombinant protein: Using genetic engineering technology, key antigenic proteins from viruses or bacteria are expressed in cultured cells (such as yeast or insect cells) outside the body. After purification, these proteins serve as the active component of vaccines. These components are highly safe and carry no risk of infection. Hepatitis B vaccines and HPV vaccines commonly use recombinant proteins.

4. Polysaccharide substances: Polysaccharide structures extracted from the surface of bacteria are used as active ingredients, primarily for preventing bacterial infections. These polysaccharides stimulate the body to produce antibodies that defend against bacterial invasion. Pneumococcal polysaccharide vaccines and meningococcal polysaccharide vaccines both use polysaccharide substances as their core active components.

5. Viral vector: The gene encoding the target pathogen’s antigen is inserted into the genome of a harmless virus (such as adenovirus), creating a recombinant viral vector. After vaccination, the vector virus expresses the antigen protein in the body, inducing an immune response. Recombinant viral vector vaccines for the novel coronavirus use this type of active ingredient.

Before vaccination, individuals should understand the vaccine's components and confirm they have no relevant allergy history; choose qualified medical institutions for vaccination to ensure proper storage and transportation of vaccines according to regulations; remain under observation for 30 minutes after vaccination, and promptly report any adverse reactions to healthcare providers—do not manage symptoms on your own.