Expanded program on immunization (EPI)
– Immunity, type of immunity.
– Vaccination program.
– Strategies of Palestinian Authority of vaccination program.
– Cold chain.
– Is the ability of the body to resist becoming infected upon exposure to a microorganisms or parasite. It is classified as:
– Non specific: (Skin, Mucosa Membrane, Phagocytosis) .
– Specific: (Active, Passive).
Types of Specific Immunity
– Active immunity
– Long-term resistance, permanent. – sometime lifelong (acquired immunity naturally or artificially)
– Is stimulation of the immune system to produce antigen – specific humeral (antibody) and cellular immunity
– Protection produced by a person’s own immune system.
– Artificially active: immunization is where the microbe, or parts of it, is injected into the person before they are able to take it in naturally.
– Naturally active: acquired through host infection, after a disease such as measles
– Short-term resistance (acquired naturally or artificially)
– Passive immunization can be naturally acquired when antibodies are being transferred from another person or animals. Such as transferred from mother to fetus during pregnancy, to help protect the fetus before and shortly after birth
Usually provide effective immunity but this immunity disappears by time.
– Artificially passive: immunization is normally given by injection and is used if there has been a recent outbreak of a particular disease or as an emergency treatment to poisons (for example, for tetanus serum).
– Natural passive: transplacental antibodies from mother to her baby and antibodies in human mil
Antigen & antibody definition
• Antigen: a live or inactive substance capable of producing an immune response, e.g. (protein, polysaccharide)
• Antibody: protein molecules (immunoglobulin) produced by B-lymphocytes to help elimination of antigen.
– The expanded program on immunization is program adopted by the WHO in 1974, it included:
1. Child immunization: immunization of children with vaccines to protected them against six-target disease.
2. Vaccination of pregnant woman with tetanus toxoid vaccine to protect woman and new born from neo – natal tetanus.
The EPI objectives
1. Reducing the incidence of the six target disease
2. Eradication the mortality rate from the sex killer disease.
3. WHO objectives polio shall be eradicated and neonatal tetanus, measles elimination
– Is one of the most successful examples of the primary prevention strategies of prevention the disease.
– Vaccination programs have been responsible for global eradication of small box and are close to elimination others (poliomyelitis, measles).
Causes of Inadequate Immunization
1. Limited access.
2. Vaccination cost.
3. Patient disinterested.
Factors Contributing to the Emergence of Infectious Diseases
– Poor, war, civil conflict, population growth, migration.
– Globalization of food supplies changes food processing, packing methods.
– Immunosuppressive drugs, organs transplantation, wide use antibiotics
– Sexual behavior, drug used, travel, diet.
– Water, flood / drought, famine, global warm.
Public health infrastructure
– Reduce prevention programs, lack communicable disease surveillance, lack of trained personnel.
Microbial adaptation and change
– Change in virulence and toxin production, development of drugs resistance e.g. Escherichia coli causes hemorrhagic colitis.
Prevention and Control of Communicable Diseases
– The goal of prevention and control programs is to reduce the prevalence of disease to level at which it no longer poses major public health problem.
– The goal of elimination is to remove a disease from a large geographical area.
– Eradication is irreversible termination of all transmission of infection by extermination of infectious agent world wide
World Health Organization
1. Reduce mortality, disability and morbidity from vaccine preventable diseases(VPD)
2. Attain the WHO of elimination and eradication.
3. Reduce undesirable outcomes of immunization.
Vaccine preventable diseases(VPDs)
Vaccine is one the most important tool of public health. VPDs are those preventable by currently available vaccines illness, disability and death of children under 5 years of age from communicable disease. The most effectively way to prevent childhood illness, death or disability is providing effectively immunization.
– Is a suspension of live or killed microorganisms are antigenic portion these agents presented to potential host to induce immunity to specific disease cause by that organism.
1. Live attenuated (Sabin- Measles–Mumps– BCG)
2. Inactivated or killed (Salk– Influenza- Rabies).
3. Cellular fraction (Pnumoccocal Pneumonia – Meningococcal).
4. Recombined vaccine(hepatitis B)
5. Toxoids or Antisera (Tetanus, Diphtheria).
6. Immunoglobulin (Hepatoglobulin)
7. Antitoxin (Tetaglobulin).
Mechanism of vaccine
Immunity against infectious diseases develops in response to antigens. antigens are molecules, which recognized by immune system and induced an immune response. an antigen stimulates the production antibodies or cellular immune response that will react specifically with that antigen. The antigens may be soluble substance produce by the microorganism or substance present on a bacterium, virus, other surface or in the cell wall. Most antigens are proteins but some are polysaccharides from bacterial capsules or glycolipids.
– Is process used to increase host resistance to specific microorganisms to prevent them from causing disease. it includes primary and secondary response in the human or animal’s body.
primary responses: occurs on the first exposure to antigen. after latent period (3 -14 days), depend on antigen.
Secondary response: is the response on second and subsequent exposure to antigen. delayed period is shorter than the primary response, the peak higher and last longer, smaller dose of antigen is required to initial response.
Immunology memory: exists even when circulation antibodies are insufficient to protect against the antigen.
Herd immunity: or community immunity describes a type of immunity that occurs when the vaccination of a portion of the population (or herd) provides protection to unprotected individuals.
Types of Vaccine
1. Live attenuated vaccine (viral or bacterial):
– Are prepared by modifying a disease – producing or bacterial in the laboratory.
– The attenuated organism has the ability to replicate and produce immunity but usually does not cause disease.
– The type of attenuated vaccines is usually prepared at laboratories by repeated culturing.
Examples of live attenuated vaccine
• Viral (measles, mumps, OPV, rubella, yellow fever).
• Bacterial (BCG, oral typhoid)
Criteria of live attenuated vaccine
• Serve reaction possible
• Reversion to pathogenic form.
• Interference from circulating antibody
2. Inactivated vaccine
Are produce by growing the bacteria or virus in culture media then inactivated it by heat and chemical (formalin).
– Types of inactivated vaccines
- Whole (virus – bacteria)
- Fractional (protein based – toxoid – subunit)
- Polysaccharide – based (pure – conjugate).
Example of inactivated vaccines
- Whole (viral influenza, polio, rabies, hepatitis B, pertussis, typhoid).
- Fractional (toxoid as diphtheria – tetanus, influenza).
- Criteria of inactive vaccines
- Cannot replicate
- Generally not as effective as live vaccines
- Immune response mostly humoral
- Antibody titer falls over time
- Principle antigen may not defined
• For live vaccines, the first dose usually provides protection, the additional doses is given to insure sero conversion. example 95%-98% of recipients will response to a single dose of measles vaccine, the second dose is given to insure that 100% of people are immune.
• For the inactive vaccine, the first dose usually does not provide protection. The proactive immune response may not develop nil second or third doses.
• Decrease the interval between doses of multi-dose vaccine may interfere with antibody response and protection.
• Live attenuated vaccine generally produces long- lasting immunity with single dose.
• The antibody titer for inactivated vaccines may decrease below protective levels after few years. (tetanus &diphtheria). So required multi doses and may required periodic boosting to maintain immunity
• Minimum interval between two live injection of the same vaccines are 4 weeks