Immunity

Immunity

Immunity is the relative ability of the body to resist almost all types of organism or toxins that tend to damage the tissues and organs.

   

Immunity is also defined as the ability of the body to recognize, destroy and eliminate the antigenic material foreign to its own. It is normally a defensive mechanism of the body.

   

Antigen: An antigen is a substance which when introduced into the system is capable of including an immune response leading to the formation of antibody with which it reacts specifically.

    

Antibody: An antibody is a modified globulin (immunoglobulin) produced in response to an antigen with which it reacts specifically.

    

Immunization: It is a technique by which immunizing agents are introduced into the body for the production of antibody to prevent diseases.

  

Toxin: It is the product of bacterial metabolism and is toxic, i.e., inhibitory or lethal to the cells of the host.

Toxin may be –

    (i) endotoxin

    (ii) exotoxin

   

Toxoid: It is a derivative of the toxin which is devoid of toxigenicity but still possessing the antigenicity.Toxic are used for the purpose of immunization.

   Examples: Tetanus toxoids, diptheria toxoids

Classification of immunity:

• Innate or nonspecific

1. Genetic
2. Mechanical
3. Humoral
4. Cellular

• Acquired or specific

a.Active

1. Natural
2. Artificial

b.Passive

1. Natural
2. Artificial

Cold chain:

Definition: Cold chain is a system of storage and transport of vaccine at low temperature maintaining their potency from the manufacturer to the actual vaccination site.

Usefulness: Cold chain is necessary because vaccine failure may occur due to failure to store and transport under strict temperature controls.

Expanded Programme on Immunization (EPI) / universal child immunization

1. Introduction

Ø  In May 1974, the WHO officially launched a global immunization programme, known as ‘Expanded Programme on Immunization’ (EPI) to protect all children of the world against six vaccine preventable diseases, namely – diphtheria, whooping cough, tetanus, polio, tuberculosis and measles by he year 2000.

Ø  In Bangladesh, EPI was formally launched on 7^th April 1979. The following Table shows the achievements and targets of EPI under 1 year in Bangladesh.

2.   National EPI Policies
3.    1. To immunize all children under one year of age throughout the country.
4.    2. To immunize all women of child bearing age including the pregnant women throughout the country.
5.    3. To extend service delivery point up to the community to cover all target population.
6.    4. To involve community level health and family planning workers as vaccination.

Table 14.13. National EPI Vaccination Schedule:

Name of the vaccine	Quantity for each dose	Interval between doses	Number of doses	Time of starting	Time of complementation
BCG	0.05ml		1	After birth	1 year
DPT	0.05ml	4 weeks	3	6 weeks	1year
HBV	0.05ml	4 weeks	3	6 weeks
OPV	0.05ml	4 weeks	4	6 weeks	1 year
Measles	0.05ml		1	After 270 days	1 year

• Vaccination should be completed within 1 year of age.
• The vaccine given before the interval between doses is uncountable and that dose of vaccine is valueless.
• Doses of OPV are 4. The 4^th dose should be with measles vaccine.
• There is no maximum limit of days between intervals of doses. If there is delay in coming to take the scheduled dose of vaccine, the vaccination should be completed according to vaccination schedule.  

Disinfection and disinfectants

• Disinfection is the killing of infectious agents outside the body by direct exposure to disinfectants.
• Disinfectants or germicide is a substance which destroys harmful microbes (not usually spores) present on the surface of inanimate objects.
• Sterilization is the process of destroying all living organism – pathogenic and non – pathogenic including their spores.
• Antiseptic is a substance which destroys or inhibits the growth of potentially infectious microorganisms.
• Disinfestations is the process of destroying small animals particularly arthropods or rodents.

Classification of disinfectants:

• Natural

1. Fresh air
2. Sunlight

• Physical

1. Heart
2. Radiation

• Chemical

1. Solid
2. Liquid
3. Gaseous