Active immunization – types of vaccines, contraindications.

Active immunity

• Natural active – infection

• Artificial active – vaccination: → development of immunological memory without infection by the pathogen and without the onset of symptoms.

• Immunity lasts for a long time.

• Development of immunity is time-consuming (days to weeks)

Active immunization characteristics

• Contains antigen

• Effect develops over days/weeks

• Long-term immunity

• Memory is formed

• Requires the ability to mount an immune response

• Both B-and T-cell response can be induced

The basis of vaccines

the microorganism as an antigen source

Vaccine contents

1. Bacteria– can be whole cell, toxoid, subunits
2. Viruses– live, attenuated, inactivated, recombinant protein, mRNA vaccines
3. Parasites– experimental vaccines (e.g. malaria vaccines)

Microbiological strategies in vaccine development

1. Attenuation
2. Inactivation
3. Toxoid formation
4. Recombinant DNA technology
5. mRNA, DNA-based approach

Types of Vaccines

• Inactivated (killed) pathogen vaccines
• Live attenuated pathogen vaccines (live bacterial cells, active virus particles)
• Subunit vaccines (antigen parts)
• Toxoid vaccine (inactivated exotoxin)
• mRNA vaccine (protein-encoding lipid nanoparticles)
• DNA vaccine (plasmid DNA)

Inactivated (killed) pathogen

A destroyed form of the entire pathogen (virus, bacteria), the antigen structure remains, the goal is to create memory cells and long-lasting protection.

Eg:- cholera, Hepatitis A

Advantages:
- Stability
- No reactivation

Disadvantages:
- Low-lasting immunity
- Time consuming to produce

Live, attenuated pathogen

Live bacterial cells with reduced virulence, active virus particles, do not cause disease, but trigger an immune response.

Eg:- MMR, Chickenpox

Advantages:
- Exactly mimics natural infections
- Cost effective

Disadvantages:
- Reactivation
- Not recommended for immunodeficiency

Subunit

Specific antigenic parts (purified proteins, polysaccharide capsule antigen).

Eg:- HPV, Hepatitis B

Advantages:
- Only a few side effects are known
- Contains antigens that trigger a targeted immune response

Disadvantages:
- Boosters needed
- Adjuvants needed

Toxoid

Inactivated (modified) form of bacterial exotoxin, unable to make the body sick, the goal is to develop immunity against the given toxin.

Eg:- tetanus, diphtheria

Advantages:
- Safe
- Strong immune response

Disadvantages:
- Booster vaccination requirement
- Adjuvant requirement (e.g. aluminum salts)

mRNA

mRNA encodes the pathogen protein, the antigen is presented, activates the immune system, including memory cells. Stronger immune response.

Eg:- COVID-19

Advantages:
- Cheap
- Strong immune response

Disadvantages:
- Storage at -70°C
- Long-term data on use are lacking

DNS

Virus or bacterial DNA integrated into a plasmid– plasmids integrated into a nanoparticle, which contains the gene of the pathogen protein, the cells of the vaccinated organism synthesize antigen from it

Eg:- SARS-COV2

Vaccination absolute Contraindications: present in all cases, the vaccine cannot be administered under any circumstances

1. Severe hypersensitivity or anaphylactic reaction to any component of the vaccine

2. Severe immunosuppression, immunological impairment

3. Pregnancy

4. Acute, severe, febrile illness

Vaccines temporary contraindications - vaccination is contraindicated, but in severe cases the purpose of saving life may override it

1. Mild infection without fever

2. Flare of chronic diseases

3. Inactivated vaccines can be given during pregnancy

4. Certain vaccines cannot be given after organ transplantation