IPC - Module 3

Question 1

Immunization is defined as…

Answer 1

Immunization is defined as a process by which resistance to an infectious disease is induced or augmented.

Question 2

What is immunity?

Answer 2

When an individual recovers from a childhood disease such as chicken pox, whooping cough or measles, they usually will not get that disease again due to development of resistance - this is immunity. The immunity has been stimulated by the disease–causing micro–organism. This stimulus is called an antigen. The host has reacted to the antigen and produced substances, resulting in immunity.

Question 3

Immunity can also be stimulated by…

Answer 3

Immunity can also be stimulated by exposing the person to the antigen artificially by giving vaccines or toxoids.

The substances most often responsible for immunity are called antibodies.

Question 4

Antigens

Answer 4

An antigen is any substance that induces a specific immune response. Antigens are also called immunogens.

Most antigens are composed of protein, but polysaccharides and combinations of polysaccharides and proteins may also be antigens.

Bacteria and viruses are antigens. Each bacterial and viral species may have several different antigens.

For example, the protein coat of a virion may be one antigen while the glycoprotein spikes of the same virion may be another different antigen

Question 5

Activation of the Immune Response

Answer 5

Depending on the antigen, either the cellular immune system (T cells) will be activated or the humoral immune system (B cells) will be activated. This results in the production of body defense products and memory cells.

Activation of the immune response occurs in the same way no matter how the antigen is introduced in to the body.

Antigen can be introduced either by:

1) naturally being exposed

2) artificially due to immunization procedures.

A combination of the cellular (T cells) and humoral immune system (B cells) combine to defend the body against cancer cells, foreign cells (incompatible blood transfusions or transplants), protozoa, fungi, bacteria and viruses.

Question 6

Antibodies are…

Answer 6

Antibodies are the result of an immune response by B cells. Antibody molecules are made up of proteins and belong to a group of proteins called gamma globulins, commonly referred to as immunoglobulins (Ig).

The two types of immunoglobulins that are important in immunization procedures are IgM and IgG.

Question 7

Immunoglobulin M (IgM)

Answer 7

IgM is the first (and largest) antibody molecule produced in the immune response. Because of their size and structure they stay in the blood stream where they have a good chance of encountering and inactivating foreign microorganisms (antigens).

They do not last long in the host and their presence indicates current or recent exposure to an antigen.

Question 8

Immunoglobulin G (IgG)

Answer 8

IgG antibody molecule follows production of IgM and is long–lasting
Its presence alone indicates past exposure to antigen
IgG is present in blood and other body fluids and comprises a major part of the humoral (fluid) immunity of the host

Question 9

Antibody Production

Answer 9

When an antigen is introduced into a host, specific lymphocytes make contact with it. Some of the lymphocytes are called T cells and others are called B cells.

The B cells are responsible for humoral immunity, or antibody production. Immunization procedures are primarily directed toward B cells and associated humoral immunity.

Once the antigen makes contact with the specific receptor on the B cell membrane, the B cell proliferates into a group of cells called a clone. These cells divide into two groups2:

Plasma cells - which produce antibodies
Memory cells - which are not currently producing antibodies but can be activated in the future to become antibody–producing cells

Question 10

Detection time

Answer 10

On first exposure to an antigen, it may take a week or longer for detectable levels of antibodies to be produced by the host.

Once the clone of memory cells is established, subsequent contact with the same antigen will give a much faster antibody response as there are more cells to recognize and respond the antigen.

The first exposure to an antigen seldom produces protective levels of antibodies while second and third exposure to the same antigen generates high levels of antibodies. Booster shots given years later will activate the immune reaction quickly and re–establish protective levels of antibodies in a short period of time.3

Question 11

Factors that Affect Response to Immunization

Answer 11

Individual differences
Not every individual responds exactly the same way to antigenic challenge. Some people have a more competent immune system than others. Differences in the immune response may be attributed to inheritance, diseases affecting the immune system and the general health of an individual. Immunization procedures provide protective levels of antibodies for most individuals, but there will be instances where the appropriate level of protection may not be achieved.

Site of injection
The recommended route of administration must be adhered to when carrying out immunization procedures. In some cases, if the antigen is delivered to tissue containing a lot of fat, the antigen may be bound to fat tissue and not reach the appropriate lymphocytes to stimulate antibody production.

Immunization product
Most immunization products have been altered and improved over the years. The objective of the changes is to improve the antibody response and to reduce adverse reactions.

Product failure
Groups of people are occasionally reported to be immunization failures. This may be attributed to a faulty lot of antigen, which could originate from the manufacturer or could be a result of improper storage. For example, some vaccines are inactivated by freezing so faulty refrigerator storage such as poor temperature regulation or shipping during a cold Saskatchewan winter could cause problems.

Question 12

Types of Immunity - innate or accquired

Answer 12

1) Innate immunity is the type that we have because of our species (human). Some diseases affect birds or animals, but not humans (e.g., chicken cholera and canine distemper).

2) Acquired immunity is any type of immunity that is not innate and is obtained during life. It may be acquired either naturally or artificially and induced either actively or passively

Question 13

Naturally-acquired immunity 3 ways

Answer 13

A consequence of a natural process such as having a disease, or
The maternal transfer of antibodies from mother to fetus via the placenta or
From mother to newborn via breast milk

Question 14

Artificially-acquired immunity

Answer 14

Antigen is administered deliberately to induce immunity, usually by injection with a needle.
There is a polio vaccine given orally and some vaccines are being developed that can be sprayed into the nose

Question 15

Active Immunity

Answer 15

The individual is given or exposed to an antigen that triggers the immune response
The individual produces his/her own antibodies
Takes days to weeks to establish protection
Used for disease prevention
Agents that induce active immunity are vaccines and toxoids
Long lasting

Question 16

Passive Immunity

Answer 16

Person given pre-formed antibodies post exposure to an antigen.
The antibodies are available immediately to provide protection
Used primarily for disease treatment, or in a few cases, short–term prevention
Products that provide passive immunity include various immune globulins, antitoxins and gamma globulin
Immunity does not last long (about 3 months)

Question 17

Products Used for Active Immunization

Answer 17

Agents used for active immunization take the form of vaccines and toxoids. The immunization product must contain the appropriate antigen to stimulate the immune response, but must also be altered in such a way that the host is not injured by the antigen.

Question 18

Vaccine

Answer 18

A vaccine is a suspension of a virus or bacteria, altered so it is not capable of causing disease, but that is still able to evoke an immune response.

In other words, it is no longer pathogenic but is still antigenic and therefore able to stimulate antibody production.

Vaccines are used for both viral and bacterial immunizations. Haemophilus influenzae and pertussis are examples of bacterial vaccines.

Measles, mumps and polio vaccines are of viral origin.

Question 19

Toxoid

Answer 19

A toxoid is prepared by extracting a bacterial exotoxin from a culture and treating it so it is no longer toxic but retains its antigenic properties. Immunization to diphtheria and tetanus is through a toxoid

Question 20

Passive Immunization

Answer 20

Products used in passive immunization consist of pre-formed antibodies (made in another person on animal such as a horse).

These products are stored in vials until they are required for disease treatment. Occasionally these products are also used for short–term disease prevention following an exposure because the antibodies are immediately available. Gamma globulin, immune globulin (specific antibodies), antiserum and antitoxin are all products containing pre-formed antibodies that may be used for immunization.

Question 21

Some examples of passive immunization include…

Answer 21

-Gamma globulin: These are antibodies from the gamma protein fraction of blood, and contain a wide variety of antibodies from a wide number of donors. These are sometimes used as protection against a variety of infections for those travelling

-Hepatitis A immune globulin: Used to prevent hepatitis A contacts from developing the disease.

-Tetanus antitoxin: Used to prevent the development of tetanus if the person has not been immunized.

-Rabies immune globulin: Part of the immunization procedure to prevent rabies.

-Anti snake venom: Used to treat snake bites.

Question 22

Active Immunity vs. Passive Immunity

Answer 22

Active Immunity
Product Given - Antigen (Bacteria/Virus, Vaccine, Toxoid)
Duration - Long (years) Person’s own immune system is stimulated, making antibodies and memory cells
Use - Disease Prevention

Passive Immunity
Product Given - Antibody (immune globulin, antitoxin, gamma globulin)
Duration - Short (3 months), Antibodies are made somewhere else (another person/horse), stored in a vial and given as required
Use - disease treatment, short term disease prevention

Question 23

Naturally / Artificially - Active / Passive Immunity

Answer 23

The immunity of a child following chicken pox is naturally–acquired active immunity.

The immunity of a child following the pertussis vaccine is artificially–acquired active immunity.

The immunity from an injection of tetanus immune globulin is artificially–acquired passive immunity.

The immunity of a newborn to infectious microbes is naturally–acquired passive immunity.

Question 24

Immunization Practices for Newborns

Answer 24

he immune system of the newborn is not well–developed and for the first two months it does not respond effectively to antigen stimulation.

During this period of time, the infant is protected by circulating maternal antibodies. At birth, the neonate has approximately the same level of protective antibodies as the mother.

The immune system of the normally–developed infant becomes competent at about two months of age, just as the protective antibodies from the mother decrease. Immunization procedures are initiated at this time.

Question 25

Immunization Practices for Healthcare worker

Answer 25

Immunization requirements for health care workers are designed to protect the patient. The province of Alberta requires that all workers have immunity to Rubella. Other immunization requirements may vary with the employer as it is their mandate to protect the patient. It is wise to check the most recent legislation and employer requirements.

Prior to the development of vaccines, communicable diseases such as measles, mumps, rubella and chicken pox were common childhood diseases. These viruses, like many others, have an incubation period of 14 to 21 days before symptoms develop.

In the 7 days before and the 7 days after the development of symptoms the organism is more easily transmitted by respiratory secretions.

In the latter stages of the convalescent period, there is generally little viral shedding. The patient was not usually isolated until symptoms appeared, so by that time many others contacts were usually infected. Hence the name, “communicable” disease. Some parents purposely exposed their children to other sick children so that they would have the disease and ultimately develop immunity.

Question 26

The routine childhood schedule in Alberta gives immunization against:

Answer 26

Diphtheria, pertussis (whooping cough) and tetanus
Poliomyelitis
Haemophilus influenzae type b
Measles, mumps and rubella
Chicken pox (Varicella)
Meningococcal disease
Pneumococcal disease

Hepatitis B is given to Grade 5 students.

Question 27

Adults - Tetanus-diptheria

Answer 27

Adults require booster shots of tetanus–diphtheria (Td) toxoid every 10 years to maintain their immunity. Memory cells that can respond to a particular antigen, tend to decrease in number after ten to fifteen years if they have not been stimulated. Booster shots serve to maintain their numbers at a protective level

Question 28

Influenza Vaccine

Answer 28

Persons over 65, as well as those who are chronically ill, are advised to have a flu vaccine each year. This vaccine is altered regularly to reflect the types of flu endemic or epidemic at the time. Other seniors with predisposition to respiratory infections may be given pneumococcal vaccine to protect against bacterial pneumonia.

Question 29

Rubella Immunization

Answer 29

Rubella immunization is important to prevent fetal infections and possible birth defects as well as eliminate the reservoir of the virus. This is the reason that both males and females are immunized.

It is the law in some provinces (Alberta included) that all health care workers have immunity to rubella. Patients are protected from contracting rubella by a visit to a health care facility – which is important not only for pregnant females, but also for other persons who may take rubella home to loved ones. Proof of immunity is either a record of immunization or demonstration of rubella antibodies (IgG) in the blood.

Question 30

hepatitis B immune globulin (HBIG)

Answer 30

The second product available for protection of health care workers is hepatitis B immune globulin (HBIG). This product contains pre-formed antibodies to hepatitis B and is a form of passive immunization.

It is used only after a blood or mucous membrane exposure to hepatitis B virus when there is no evidence of anti HBs immunity in the health care worker. The “no evidence” could come from a negative antibody test or no test results available.

HBIG should be given within 48 hours of exposure as the effectiveness diminishes with time. This passive immunization should provide protection for the current incident and a vaccination program should be started to cover future blood encounters.

Both HBIG and hepatitis B vaccine are used to treat babies born to mothers who are positive for hepatitis B virus. The combination of active and passive immunization will protect the infant from infection. This is a very cost–effective measure as many of these children will otherwise become hepatitis carriers and eventually die of liver disease.

Question 31

Immune Status to Chicken Pox

Answer 31

Chicken pox (varicella) is caused by a virus belonging to the herpes group called varicella–zoster virus. The infection is spread from person to person, directly or indirectly, by contact with respiratory secretions or vesicular fluid. The incubation period is two to three weeks.

Chicken pox is a generalized infection characterized by fever, malaise and vesicular eruptions. The chicken pox vesicles are raised, filled with fluid and itch. The illness tends to be more severe in adults. Babies born to women in whom chicken pox develops within five days of delivery are likely to have a very severe case of the disease.

There is a ten times greater risk of developing necrotizing fascitis (flesh eating disease) when Streptococcus pyogenes invades chicken pox lesions. This is the reason why varicella immunization of children has been promoted by Public Health.

Question 32

Tuberculosis

Answer 32

Tuberculosis has been one of the great afflictions of mankind but has declined dramatically in the second half of this century and in developed countries due to better drugs and improved living conditions. Tuberculosis continues to remain a major infectious disease in undeveloped countries due to overcrowding, poor living conditions and poor nutrition.

Question 33

Tuberculosis (TB) Now

Answer 33

The approximate 1.5 million deaths annually make it the most frequent cause of mortality due to a single pathogen. The most dramatic increases since the 1980’s are seen in countries where rates of HIV infection (the causative agent of AIDS) are rising unabated.

Canada is one of the few countries of the world reporting fewer than 10 TB cases per 100,000 persons. Since 1987, the rate has stabilized at about 5 cases per 100,000 persons. Although rates have not increased, a plateau has been reached, ending years of decreasing rates and prompting intensive re-evaluation of the TB situation.
In Canada, people at higher risk of having active TB than the general population include foreign-born individuals from countries reporting high TB rates, Indigenous Peoples, poor and homeless people, alcohol and drug abusers, elderly people and AIDS patients.
A concern with the plateau of TB is the appearance of drug resistant strains. Some strains of the tubercle bacillus that have been isolated are dangerously close to being untreatable with drugs currently available.

Question 34

TB can pose a risk to health care workers. The risk can be minimized as follows:

Answer 34

Recognize high-risk patients that may have tuberculosis
Understand how tuberculosis is spread
Use of tuberculin skin testing
Use of anti-tuberculosis drugs when appropriate

Question 35

Spread of TB

Answer 35

TB is transmitted by the inhalation of airborne organisms from the respiratory secretions of patients with pulmonary tuberculosis.

Direct Contact
When a TB patient coughs, fairly large globs of sputum may be discharged into the surrounding air. These globs may be inhaled by a person at close range but this is not as dangerous as it seems. Large particles are effectively removed by the cilia lining the mucus-lined airways. The particles are trapped in the sticky mucus and propelled up and away from the lungs by the cilia. But, there is still a chance of the bacteria reaching the lungs especially if a lot of respiratory secretions are inhaled.

Droplet Nuclei
The greatest danger of being infected with tubercle bacilli comes from the inhalation of droplet nuclei. Sputum and respiratory secretions expelled by a TB patient dry in the outside environment to form microscopic particles (droplet nuclei) that float freely in the air. The tubercle bacillus has a waxy cell wall that allows it to remain viable in dry conditions. The droplet nuclei may each contain several live bacteria. When these are inhaled, they usually reach the lung as they are small enough to avoid the defence system of the upper airway.

Question 36

After Inhalation of the TB Bacteria

Answer 36

Tubercle bacteria that do reach the lung multiply slowly there for 3-6 weeks until the cellular immune system is fully activated. Once this happens, the body is able to inhibit growth of the bacteria and the infection is halted. This is the scenario for over 90% of people inhaling tubercle bacilli. They are infected with the bacteria but never have the disease. They will likely never know they have encountered the bacteria and will not pass the bacteria on to other people.

Approximately 5% of people infected with tubercle bacilli will develop an active case of TB. A number of factors contribute to this: poor nutrition, crowded living quarters and certain racial types. A compromised immune system is the single most important factor contributing to active tuberculosis. The patient with AIDS tops the list of those likely to later develop the disease after inhaling tubercle bacilli.

Another 5-10% of people infected with tubercle bacilli will develop TB some time later in life. Even though the cellular immune system has effectively stopped multiplication of the bacteria by enclosing the organisms in a mass of cells called a granulomata resulting in a small focus of viable (live, but inactive) bacteria remaining in their body. These bacteria may reactivate when the immune system breaks down and the protective mass of cells is no longer maintained in the body. AIDS patients are a prime candidate for this occurrence.

Question 37

Percentage of those infected with TB

Answer 37

90% infected but no disease
5% active disease
5-10% infected, then develop disease later in life

Question 38

Symptoms of TB

Answer 38

The classical presentation for a patient with tuberculosis is:

persistent cough
fever
malaise
weight loss
Initial sputum production may be scant, but as the infection progresses in the lungs, lager amounts with blood is common. The infection spreads from the lungs to other parts of the body and death may result from dysfunction of multiple organs.

Question 39

Tuberculin Skin Test (TST) - Mantoux Test

Answer 39

The tuberculin skin test has proven to be an effective method of identifying individuals infected with tubercle bacilli. The test involves the intradermal injection of a small amount of tubercle protein in the forearm. The test is read at 48-72 hours and a positive is indicated by a raised, hard area at the site of injection.

Description: The Mantoux skin test is given with a needle and syringe used to inject testing fluid, called tuberculin, between the layers of the skin (usually forearm). The injection site becomes hard (indurated), and red in a person whose immune system has been exposed to tuberculosis.

Question 40

Reasons for a positive tuberculin skin test

Answer 40

The person has an active case of tuberculosis. A visit to the doctor, a chest X-ray and a sputum culture will confirm this.

The person has been in contact with and been infected but the bacteria have been effectively controlled by the immune system (often walled-off in a granulomata). The person does not have active tuberculosis disease and is not infectious, however, some (5-10%) may develop active disease later in life if their immune system becomes compromised (e.g., AIDS patients).

The person has had an active case of tuberculosis in the past. This person will know they have had the disease, will have been treated and will no longer be infectious. These people should not be tuberculin skin tested, but rather have chest X-rays.

The person has been immunized against tuberculosis. The vaccine called BCG that is given in many countries, but not routinely in Canada. It is given to many children whose health services are looked after by the Government of Canada Medical Services, which includes most children on northern reserves. It may provide some degree of protection against TB and will result in a positive tuberculin skin test for a variable period of time.

A positive Tuberculin Test means that somehow, sometime, somewhere the patient has been exposed to the tuberculosis bacteria either naturally or through immunization. It does not mean that the person necessarily has an active case of the disease.

Question 41

immunity definition

Answer 41

immunity: resistance to a specific disease

Question 42

antigen definition

Answer 42

antigen: “substance” that induces the immune response, e.g., bacteria, viruses

Question 43

Antibody definition

Answer 43

antibody:“products” of immune response; globulin type of protein

Question 44

immunoglobulin definition

Answer 44

immunoglobulin: – an antibody, immune globulin, Ig

Question 45

IgM definition

Answer 45

first antibody produced in immune response
indicates current or recent infection or exposure to antigen

Question 46

IgG definition

Answer 46

second antibody produced in the immune response
indicates past infection (when IgM absent)

Question 47

Antibody production

Answer 47

1. Antigenic stimulation of B cells (lymphocytes) yields:
   clone of antibody–producing cells (plasma cells) clone of memory cells (ready to jump into action if the same antigen comes along again)
2. Immune response after primary immunization:
   no detectable antibodies for a week or longer
   a small burst of IgM antibodies occurs first
   a small burst of IgG antibodies follows
3. Immune response after second, third, and booster shots:
   almost immediate response due to activation of memory cells
   a small burst of IgM
   a large burst of IgG provides protective levels of antibody

Question 48

Factors Affecting Response to Immunization

Answer 48

1. Differences in immune response by host
   inheritance
   diseases affecting immune system
   general health
2. Site of injection
   type of tissue
   fat may absorb antigen so it does not reach B cells
3. Immunization product
   manufacturers striving to improve vaccines and toxoids to give better immune response and fewer adverse reactions
4. Product failure
   bad batch from manufacturer
   improper storage may inactivate

Question 49

Products used for immunization

Answer 49

1. Vaccine: suspension of bacteria or virus, altered so not able to cause disease but still antigenic … causes production of antibodies
   e.g., pertussis vaccine, measles vaccine
2. Toxoid: bacterial exotoxin treated so no longer toxigenic (harmful) but still antigenic … causes production of antibodies
   e.g., diphtheria toxoid, tetanus toxoid

Question 50

Types of Immunity

Answer 50

1. Artificially acquired:
   product given for the purpose of providing immunity … usually means a needle
2. Naturally acquired:
   an act of nature such as having a disease or antibodies transferred from mom to baby

3.Passive immunity:
host given preformed antibodies
protection available immediately
used for disease treatment and occasionally short term prevention

4. Active immunity:
   host makes own antibodies when given or exposed to antigen
   antibodies not available for days or weeks (takes longer if this is first exposure to antigen)
   used for disease prevention … long term