Immunoprophylaxis

Historical stages of vaccination development

Attempts to protect humans from severe infections were undertaken long before immunology formed as a full-fledged academic discipline. It was the success in developing vaccination methods that laid the foundation for the development of modern immunology as a whole.

The main milestones in the development of immunoprophylaxis can be divided into several key stages:

1. Ancient stage (about 3,000 years ago). The first written evidence of attempts to prevent infections comes from Asia. There, variolation was used—inoculating healthy people with material from patients with mild smallpox.
2. Late 18th century. The English physician Edward Jenner made a breakthrough by developing a relatively safe method for preventing smallpox. As an immunizing agent, he used material from cows infected with cowpox, which provided cross-immunity in humans.
3. 1880 and the era of Louis Pasteur. The prominent French scientist formulated the fundamental principles of vaccination using chicken cholera as an example. He was the first to use a live attenuated vaccine. Pasteur is also credited with creating the rabies vaccine, which is unique in that it provides protection even after infection (an animal bite).

In subsequent years, the process of creating new vaccines became continuous, and the immunoprophylaxis procedure itself was strictly regulated and codified at the legislative level.

Evolution of the term "Vaccine"

As science progressed and the range of immunobiological agents expanded, the very concept of a vaccine underwent significant changes. Today in medicine, it is customary to distinguish between the classical and modern (expanded) definitions of this term.

Classic definition: Vaccines are specific biological products whose primary goal is to induce protective immunity and immunological memory against antigens of specific pathogens. The key feature here is establishing protection while bypassing the full-blown infectious disease stage. Accordingly, vaccination in the classical sense is a method of generating such immunity through the administration of vaccines.

Modern (expanded) definition: Today, vaccines are preparations containing antigenic material aimed not only at preventing but also at treating various pathological conditions by inducing effector and memory cells.

This expansion of the term is directly related to the fact that modern immunobiological agents are used not only against infections. They are actively developed and utilized for:

• combating neoplastic processes (antitumor vaccines);
• therapy of allergies (anti-allergy vaccines);
• treatment of autoimmune diseases.

Thus, the focus has shifted from exclusively prophylactic application to widespread therapeutic use in immune-mediated disorders.

Live attenuated vaccines

This is historically the first variant of classical vaccines introduced into routine medical practice by Louis Pasteur. Despite the antiquity of this concept, such preparations still hold a vital place in immunization schedules due to their high efficacy.

Production method and mechanism of attenuation To create such a vaccine, the microorganism (pathogen) is cultivated for a long time in artificial, unfavorable conditions. During adaptation to the new, altered habitat, the microorganism undergoes a series of mutations. The traits necessary for its survival in the host organism (primarily pathogenicity and virulence) provide no evolutionary advantages under laboratory conditions. As a result, these aggressive properties are naturally lost, which is termed attenuation.

Pros and cons

• Advantages: Live vaccines closely mimic the natural infectious process (without causing severe disease); therefore, they typically exhibit exceptionally high immunogenicity and induce robust, long-lasting immunity.
• Risks: The main and ever-present disadvantage of such preparations is the risk of reversion. This is a process whereby the mutated attenuated microorganism can regain its original pathogenicity and virulence, potentially leading to infection in the vaccinated individual.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Mechanisms of immunological memory formation during vaccination
• Principles of developing antitumor vaccines
• The role of effector cells in post-vaccination immunity
• Features of post-exposure prophylaxis using rabies as an example
• Therapeutic vaccines for the treatment of autoimmune diseases

Other topics in the section "Immunity in defense and damage of the organism. Pathology of immunity"

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