What a vaccine preparation consists of
Any vaccine is a complex immunobiological complex. In addition to the main active substance (specific antigen), the composition includes auxiliary components that depend on the dosage form:
- Stabilizers. Protect the antigen from degradation during production and long-term storage. Examples include a sucrose-agar-gelatin mixture or homologous proteins (human albumin).
- Preservatives. Ensure solution sterility and inhibit the growth of accidentally introduced microflora. Formalin, thiomersal (at a dilution of 1:10,000), and other antimicrobial agents are used for this purpose.
- Adjuvants. Substances that nonspecifically enhance the immunogenicity of the administered antigen, forcing the body to mount a stronger immune response.
Live vaccines
The active principle here is attenuated (weakened) strains of microorganisms. They are completely devoid of virulence (cannot cause disease) but retain specific antigenicity.
Methods of pathogen attenuation:
- Chemical — treatment with mutagens.
- Physical — exposure to radiation or temperature.
- Biological — prolonged passages (subculturing) of the pathogen through cell cultures, chicken embryos, or the bodies of susceptible animals.
The essence of a live vaccine's action is that microorganisms with residual virulence multiply within the human body. This safely mimics a real infectious process and leads to the development of robust immunity. Such preparations are dosed by the number of live microbial cells or viral particles and are administered, as a rule, as a single dose (e.g., vaccines against measles, rubella, mumps, poliomyelitis).
In addition to classical attenuated strains (originally proposed by Pasteur), divergent strains are used — human-safe related microbes (bovine mycobacteria for BCG, cowpox virus). There are also vector vaccines, where genes for protective antigens are genetically engineered into the genome of a safe carrier (e.g., vaccinia virus or Salmonella).
Inactivated (killed) vaccines
These preparations contain no live pathogens. They are divided into two large groups:
- Whole-cell / Whole-virion: contain entirely killed bacteria or viruses.
- Subcellular / Subvirion: contain only extracted complexes with the necessary protective antigens (proteins, glycoproteins, lipopolysaccharides).
Pathogen inactivation is carried out using chemical methods (phenol, alcohol, formaldehyde) or physical methods (ionizing radiation, UV irradiation, heating). To isolate antigens in subcellular vaccines, enzyme treatment, phenol extraction, ultracentrifugation, isoelectric precipitation, chromatography, and ultrafiltration are applied.
Unlike their live counterparts, inactivated vaccines are dosed in antigenic units. Their composition almost always includes adjuvants and preservatives. They are administered parenterally (intramuscularly, subcutaneously), and a course of multiple injections is required to establish reliable immunity.
Safety requirements and contraindications
Before entering mass use, a preparation must meet strict criteria. The modern approach dictates: whether a vaccine is live or killed, the main thing is the maximum protective effect (reduction in morbidity) without compromising the patient's health.
Biological requirements:
- High immunogenicity.
- Areactogenicity (absence of severe adverse reactions).
- Genetic stability of vaccine strains.
- Absence of oncogenic, allergenic, and teratogenic (fetal-damaging) properties.
Contraindications (medical exemptions) are established to prevent post-vaccination complications. General medical exemptions include: acute infectious and non-infectious diseases, pronounced immunodeficiencies, severe cardiovascular pathologies, malignant neoplasms, chronic parenchymal organ pathologies, CNS diseases, and allergic conditions. At the same time, local manifestations (hyperemia, edema) or short-term fever within normal limits are not a reason to refuse further vaccinations.
Legal regulation and immunization schedule
In Russia, immunization is regulated by the Federal Law "On Immunoprophylaxis of Infectious Diseases" and the National Immunization Schedule.
The schedule justifies the age-based administration schemes for preparations. The mandatory list for children (under 10 years old) and adults includes vaccinations against tuberculosis, hepatitis B, poliomyelitis, pertussis, diphtheria, tetanus, measles, rubella, and mumps. Additionally, vaccination is carried out for epidemiological indications (e.g., against influenza) or when staying in areas endemic for particularly dangerous infections.
Briefly: answers to topical questions
What specific substances are used as adjuvants in vaccines?
Aluminum compounds are used as adjuvant-sorbents to increase the immunogenicity of toxoids:
- Aluminum hydroxide gel ($Al(OH)_3$).
- Aluminum phosphate ($Al(PO_4)$).
They are added to purified toxoid to obtain purified adsorbed toxoids.
Which infections are included in the mandatory list of the National Immunization Schedule of the Russian Federation?
The mandatory list of the National Immunization Schedule includes:
- tuberculosis;
- hepatitis B;
- pertussis, diphtheria, tetanus;
- poliomyelitis;
- measles, rubella, mumps.
In addition, since 2011, vaccination against Haemophilus influenzae infection has been included in the National Immunization Schedule.
What absolute and false contraindications to vaccination exist?
The sources do not provide a classification of contraindications into absolute and false. General medical contraindications are listed:
- acute infectious and non-infectious diseases;
- allergic conditions;
- central nervous system diseases;
- chronic pathologies of parenchymal organs, including the liver and kidneys;
- severe cardiovascular diseases;
- pronounced immunodeficiencies;
- malignant neoplasms.
An absolute contraindication to vaccination with any live vaccines after kidney transplantation is the post-kidney transplant state. BCG is strictly contraindicated in children with HIV infection.
Live vaccines "live" (multiply in the body, usually administered once); killed vaccines require more effort (adjuvants added, a course of injections needed).
Class and exam questions
What is the main difference between live and inactivated vaccines?
Live vaccines contain attenuated strains capable of multiplying within the body and safely mimicking the infectious process. Inactivated vaccines contain killed microorganisms or their fragments, cannot multiply, and usually require a course of multiple injections.
What are divergent strains?
These are non-pathogenic microorganisms for humans that share protective antigens with dangerous pathogens. Classic examples include the use of the cowpox virus or Mycobacterium bovis (in the BCG vaccine).
Are fever and redness considered an adverse event following vaccination?
Short-term fever, as well as edema and hyperemia at the injection site, are considered acceptable post-vaccination reactions. If their severity does not exceed the parameters in the product labeling, vaccination may be continued.
What else to study on this topic
- Methods for isolating antigenic complexes for subcellular vaccines (ultrafiltration, chromatography)
- Principles of development and mechanism of action of vector (genetic engineering) vaccines
- National Immunization Schedule: age-based schedules
- Differential diagnosis of acceptable reactions and post-vaccination adverse events
- Promoting trends: therapeutic vaccines for oncology and substance dependence
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