Diseases and Infections

Immunisation Immunisation is a process that helps the body’s immune system fight against infectious diseases. It involves introducing a small piece of a pathogen, which could be a virus or a bacterium, in its weakened or killed form into the body. These weakened or killed pathogens are called immunogens. They provide immunity by triggering the immune system to produce antibodies and immune cells. These antibodies and immune cells recognise and attack the pathogen if the body is exposed to it in future. Immunisation is usually carried out artificially but can also be achieved naturally when a person encounters a pathogen.

Immunisations are of two types. These are active immunisation (which involves the introduction of vaccines into the body to stimulate the immune system to produce antibodies) and passive immunisation (which involves acquiring pre- formed antibodies, e.g. a mother passing on antibodies to her newborn).

Although both forms of immunisation provide immunity, it is important to note that active immunisation is more permanent while passive immunisation is temporary.

Figure 3.47: A male adult being immunised through injection.

Steps Involved in Immunisation

The steps involved in immunisation are as follows:

1. Introduction of an antigen (a harmless piece of a pathogen) into the body.

2. Recognition of antigen by immune cells (T-cells and B-cells) of the immune system.

3. Activation of immune response (process by which the body’s immune system recognises and responds to the presence of foreign substances such as pathogens).

4. Production of antibodies and immune cells.

5. Memory cell formation for future protection (whenever the same kind of antigen enters the body again, the immune system uses the memory cells to recognise it and produce antibodies against it).

Antigens may or may not stimulate an immune response. However, when introduced intentionally as immunogens, their purpose is to produce an immune response. This explanation points to the fact that all immunogens are antigens, but not all antigens are immunogens, as immunogens induce an immune response, whereas antigens may not.

Vaccination Vaccination is the act of administering a vaccine into the body of an individual to stimulate the body’s immune system to produce antibodies against a specific pathogen. The vaccines usually contain weakened or killed pathogens or components of pathogens (e.g. proteins or sugars). Vaccines work by stimulating the body’s immune system to recognise and fight the pathogen, in so doing providing active immunity, meaning the body produces antibodies to fight the disease. Apart from the commonly known forms of vaccines (live but weakened or killed pathogens), vaccines could also be in the form of toxoid (mRNA-based vaccines).

An infant receiving a vaccine orally A child receiving a vaccine through injection

Figure 3.48: Images of children receiving a vaccination Steps involved in vaccination

1. Production of a vaccine by processes such as attenuation and inactivation.

2. The vaccine is introduced into the body orally, through the nasal route or by injection.

3. The body’s immune system responds to the vaccine by producing antibodies and memory cells.

4. The specific antibodies produced now fight the pathogen.

Differences between Vaccination and Immunisation

1. Vaccination is a specific intervention involving administering a vaccine, while immunisation is acquiring immunity.

2. Vaccination induces active immunity, while immunisation can result from active or passive immunity.

3. Vaccination is a medical intervention (involves the use of vaccines) while immunisation can occur naturally or through medical means.

Inoculation This is the introduction of a substance or an agent to a material. The term is applicable in various fields. For example, in agriculture, inoculation is used to introduce beneficial microorganisms into soil, plants or seeds to improve nutrient uptake or induce disease resistance. In medicine, however, inoculation is a medical procedure where a pathogen or antigen is intentionally introduced into the body to induce immunity. In earlier years, it was done by collecting antigens from sores developed from smallpox and introducing them into healthy individuals to induce immunity. In modern times, this can be done through various methods, including exposure to a mild form of the disease, injection of a small dose of inactivated or weakened pathogens or administration of antibodies or immune cells. The goal of inoculation is to stimulate the immune system to produce antibodies and immune cells that can recognise and fight the pathogen.

Steps involved in inoculation

1. A mild form of the pathogen is obtained from a sick person’s wound or lesion.

2. The pathogen is weakened through processes such as heating or chemical treatment.

3. The skin of a healthy person was scratched or pricked to create a small wound.

4. The healthy person was observed for signs of infection and disease progression.

5. The body of the individual reacts by producing antibodies which fight the pathogen and therefore bring about recovery.

Note

While this method was principally the means of acquiring immunity in historic times, it was a risky method and sometimes resulted in full-blown disease or transmission to others.

Figure 3.49: A child being inoculated against smallpox by Edward Jenner.

Differences between Inoculation and Vaccination

1. Scope: Inoculation is a broader term that includes various methods of introducing pathogens or antigens to induce immunity, while vaccination specifically refers to the use of vaccines.

2. Method: inoculation may involve exposure to pathogens through various routes, such as the skin and mucous membranes, while vaccination typically involves injection or oral administration of vaccines.

3. Safety: inoculation has a higher risk due to the use of weakened pathogens, while vaccination is generally considered safer than inoculation because vaccines are carefully tested and regulated to ensure safety and efficacy.

4. Effectiveness: Vaccination is a modern practice often more effective in providing long-term immunity because it uses refined and regulated vaccines, while inoculation is a less popular health practice and was used in the control of smallpox.

5. Purpose: inoculation may be used for research or therapeutic purposes, while vaccination is basically for preventive purposes.

Activity 3.23 Understanding Immunisation, Vaccination and Inoculation

1. Get together with three or four of your friends and research one of the following terms: immunisation, vaccination and inoculation for the definition of your assigned term.

2. Discuss with your friends and write your definition on sticky notes or a sheet of paper.

3. Read out your group’s definition to the hearing of the rest of the class.

4. With your friends, get a large sheet of paper or cardboard and use diagrams, flowcharts or illustrations to create a mental picture to describe the steps involved in carrying out your assigned term, i.e. immunisation, vaccination or inoculation.

5. Compare your work with members of the other groups in your class.

6. Identify similarities and differences between your work and those of other groups.

7. Engage in a class discussion facilitated by your teacher with members from other groups to clarify any misconceptions.

Importance of Immunisation, Vaccination and

Inoculation The importance of immunisation, vaccination and inoculation can be grouped under the following broad headings:

1. Individual benefits: the prevent serious illnesses and diseases polio, measles, hepatitis B and yellow fever, by boosting the immune system, also reducing the chances of hospitalisation and the risk of serious complications.

2. Community benefits: vulnerable individuals (newborns, the elderly and those with compromised immune systems) are protected through herd immunity. It also reduces disease transmission and outbreaks and protects future generations through lasting immunity. It decreases disease-related mortality rates and supports economic growth by reducing healthcare costs.

3. Global benefits: diseases such as smallpox and poliomyelitis have been controlled, and others such as measles and malaria. Also, international travellers can travel to disease-endemic areas without the fear of catching infections such as the dreaded COVID-19 disease.

4. Social benefits: people can freely associate with family and friends and have equal access to services without the fear of being infected. Furthermore, vulnerable populations like children and the elderly are protected. Finally, it supports education and social development.

Activity 3.24 Immunisation forum Your teacher will invite the community health nurse or public health nurse to deliver a talk on immunisation, vaccination and inoculation. Listen attentively and ask questions where necessary.

1. Write out your presentation to be delivered before your classmates in class under the following headings:

a. Introduction

b. Immunisation, vaccination and inoculation

c. Differences between immunisation, vaccination and inoculation.

d. Reasons why immunisation, vaccination and inoculation are important among humans.

2. Try and answer questions from your friends as best as you can. Consult with your teacher if you are not sure.