Vaccine administration

Routine immunization: schedule and timing

Dosages and intervals between vaccinations are strictly regulated. There are two main stages:

• Primary immunization: includes 2–3 injections given at 4-week intervals.
• Booster immunization: carried out several years later to maintain and enhance the protective effect.

The administration schedule in the first years of life depends on the type of pathogen. In the first days after birth, infants receive protection against tuberculosis (BCG) and hepatitis B. At the age of three months, the DTaP vaccine is administered. Antiviral preparations are prescribed much later—at 12–15 months. This delay is necessary to prevent maternal antibodies present in the infant's blood serum from neutralizing the administered antigen.

The primary delivery route for preparations is subcutaneous, with intramuscular use being less common. Mucosal forms (nasal and oral) are also currently under active development.

Vaccination features in bleeding disorders

Vaccination is not contraindicated in patients with hemophilia and other blood coagulation disorders. Protection against hepatitis B is of particular priority for this group.

Oral and subcutaneous routes are considered optimal. Intramuscular and intradermal injections are highly discouraged due to the risk of tissue trauma. If the intramuscular route is the only available option, strict rules must be followed:

1. Replacement therapy is mandatory to prevent hematoma formation.
2. Replacement therapy products are administered strictly the day before the procedure.
3. Administration of hemostatic drugs on the day of vaccination itself is not recommended.

Active bleeding is an absolute contraindication for any injections.

Side effects and complications

Vaccination reactions are divided into expected side effects and severe complications.

Frequent side effects include general malaise, moderate fever, and local reactions at the injection site. Headaches, joint pain, sleep disturbances, vomiting, and fainting are less common. The etiology of such conditions is associated either with impurities in the preparation or the action of pro-inflammatory factors from the active component itself (e.g., the pertussis component in DTaP).

Severe complications are extremely rare (mortality is about 1:1,000,000). These include:

• Post-vaccination infectious process (caused by live attenuated pathogens).
• Toxic reactions.
• Allergic conditions.
• Nervous system lesions.

Despite the risk of isolated complications, the global impact of vaccination is undeniable: it has radically reduced child mortality and freed humanity from deadly epidemics.

Biological method (In vivo)

The biological method is used to evaluate vaccine efficacy, study the immune response, and isolate pathogens. It is based on the experimental infection of sensitive laboratory animals (mice, rats, guinea pigs, rabbits).

Methods of material administration to animals:

• Enteral (via the mouth).
• Respiratory (into the respiratory tract).
• Parenteral (intravenous, intraperitoneal, subcutaneous, intramuscular, intradermal).
• Into special loci (subdural, into the anterior chamber of the eye, suboccipital).

The main advantage of the method is the ability to isolate microorganisms that do not grow on artificial media. In addition, the In vivo method allows evaluation of pathogen virulence, modeling of the infection clinical picture, and testing of antimicrobial drug activity.

Class and exam questions

What else to study on this topic

• Characteristics of mumps, rubella, and hepatitis vaccines (antigen nature, adjuvants, preservatives)
• Classification of post-vaccination complications (toxic, allergic, neurological)
• Criteria for selecting laboratory animals for the biological method
• Mechanisms of humoral immunity development during vaccination

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.