Viral vaccines

Classification of viral vaccines

Depending on production technology and the state of the pathogen, several groups of vaccine preparations are distinguished:

• Live attenuated. Contain weakened but viable strains of the virus. They induce the most robust and intense immunity, which is as close as possible to natural post-infection immunity. This group includes the oral polio vaccine (OPV), as well as vaccines against measles, rubella, and mumps.
• Inactivated (killed). Do not contain live pathogens. They have lower reactogenicity, but require repeated administrations to maintain reliable protection. An example is the inactivated polio vaccine (IPV).
• Recombinant. Created using genetic engineering methods (e.g., hepatitis B virus vaccine).

According to their composition, preparations are divided into monovalent vaccines (protecting against a single infection) and polyvalent/combination (e.g., measles-mumps bivalent vaccine or combination preparations including components against poliomyelitis and Haemophilus influenzae type b).

Influenza vaccine prophylaxis

Specific prevention of influenza is carried out annually. The optimal timing is a month before the start of the epidemic season (in October–November). Vaccination is strictly indicated for risk groups: children, individuals over 65 years of age, pregnant women, patients with chronic diseases, and healthcare workers. Due to the variability of the virus, the strain composition of vaccines is updated every 2–3 years based on epidemiological forecasts.

Modern influenza vaccines are divided into several types according to the degree of purification:

1. Live allantoic. Administered intranasally. Stimulate the production of full-fledged immunity, including local secretory IgA. The main disadvantage is the risk of allergy to chicken protein.
2. Inactivated whole-virion. Administered parenterally, but also retain the risk of allergic reactions to chicken embryo protein.
3. Split vaccines. Contain the full spectrum of viral antigens, however, the lipids of the outer envelope are removed from them, which significantly reduces the pyrogenic effect.
4. Subvirion (split/subunit). Highly purified preparations containing only key protective antigens — hemagglutinin (HA) and neuraminidase (NA).
5. Polymer-subunit. New-generation vaccines with immunomodulating effects due to the inclusion of adjuvant polymers.

Prevention of viral serous meningitis

Viral serous meningitis in most cases develops as a secondary complication of other infections. Therefore, their specific prevention comes down to routine immunization against the primary pathogens:

• Mumps. CNS involvement is one of the typical complications. A live vaccine is used for protection, administered to children over one year of age (infants up to 6 months are protected by maternal antibodies).
• Poliomyelitis. The meningeal form is prevented by routine administration of IPV or OPV.
• Measles, rubella, and chickenpox. The use of live vaccines against these infections reliably reduces the risk of secondary meningitis.

For enterovirus infection (Coxsackie and ECHO viruses), mass specific vaccination is not carried out. Emphasis is placed on nonspecific measures: early isolation of patients, medical supervision of contacts, and a strict sanitary-hygienic regimen in groups.

Features of the National Immunization Schedule

The National Schedule regulates strict administration regimens for preparations to build herd immunity:

• Hepatitis B. The standard regimen includes three doses: 0–1–6 months. The first injection is given in the first hours of a newborn's life.
• Poliomyelitis. Vaccination starts at 3 months. The first two doses must be administered with an inactivated preparation (IPV), while the third and subsequent revaccinations are done with a live vaccine (OPV). In closed children's institutions (orphanages, boarding schools), exclusively IPV is used to eliminate the risk of vaccine-associated complications.
• Measles, rubella, mumps. Vaccination is performed at 12 months with revaccination at 6 years. Measles vaccines are administered subcutaneously (0.5 ml) and are approved for use regardless of the patient's existing immunity to rubella or mumps.
• Rubella catch-up strategy. This is supplemental immunization of unvaccinated children, adolescent girls, and women aged 18–25. Its main goal is to protect pregnant women and prevent congenital rubella syndrome.

Class and exam questions

What else to study on this topic

• Emergency vaccination regimens for epidemic indications (COVID-19, hepatitis A).
• Anti-epidemic measures and timelines for group isolation during influenza outbreaks.
• Bacterial vaccines: toxoids and acellular preparations.
• Age restrictions for diphtheria and tetanus revaccination (transition to Td-M).
• Nonspecific prevention of enterovirus infection in children's groups.

Other topics in the "Additional Topics" section

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