Childhood Immunisation, Slides of Pediatrics

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Childhood immunization

Seminar 1

Describe active and passive immunity

Type of Immunity Active Immunity Passive Immunity

Definition The protective immunity in which the individual’s own immune system is stimulated to produce antibodies and lymphocytes

The immunity in which a person receives antibodies or lymphocytes that have been produced by another individual’s immune system

Natural Acquirement Arise naturally when an individual is exposed to an antigen or pathogen (clinical infection)

Arise naturally when a fetus receives antibodies from the mother across the placenta or when a breast-feeding infant ingests antibodies in the mother’s milk.

Durability The protection offered is long-lived The protection offered is long-lived.

Antibody production Involves antibody production which is induced by infection or immunogen

No antibody is produced, but directly transferred

Memory cell formation Active immunity results in the formation of long-lasting memory cells

Memory immune cells are not formed.

Response time The protective response takes time to establish as a lag period is present

No lag period hence the protection is instant.

Example Natural producing antibodies in response to exposure to a pathogenic infection such as measles or cold

Natural Receiving antibodies from another organism (e.g. to the foetus via the colostrum or a newborn via breast milk).

Artificial Producing antibodies in response to the controlled exposure to an attenuated pathogen (vaccination)

Artificial Receiving manufactured antibodies via external delivery (e.g blood transfusions of monoclonal antibodies).

● Vaccines contain the same antigens or parts

of antigens that cause diseases, but the antigens in vaccines are either killed or greatly weakened.

● When they are injected into fatty tissue or

muscle, vaccine antigens are not strong enough to produce the symptoms and signs of the disease but are strong enough for the immune system to produce antibodies against them.

● The memory cells that remain prevent

re-infection when they encounter that disease in the future. Thus, through vaccination, children develop immunity without suffering from the actual diseases that vaccines prevent.

Vaccine Classification

Classified into:

A. Live, Attenuated

● Derived from “wild” viruses/bacteria ● Wild viruses/bacteria → Attenuated (weakened) in Lab (by repeating culturing) e.g. Measles virus was isolated from a child with measles disease in 1954 (~10 years of serial using tissue culture → Transform wild measles virus into attenuated vaccine virus. ● Fragile; damaged/destroyed by heat and light (Must stored and handled carefully) ● Attenuated vaccine:

• Replication in body → trigger immune response (able to cause disease but mild)
• Attenuated vaccine virtually identical to natural infection by wild virus.
• May cause severe/fatal infection → Uncontrolled replication of vaccine virus/bacteria (often occur if weakened immune system)

Vaccine Classification

i. Whole-cell inactivated vaccine - contain bacteria/viruses (Killed through physical/chemical process)

• e.g. Polio vaccine, HepA, Rabies, Pertussis

ii. Subunit vaccines - Contain portion of bacteria/virus

• Antigen: Protein, polysaccharide, combination of these two

iii. Conjugate subunit vaccine - chemically attaching polysaccharide (from surface of bacteria) to a protein molecule thru conjugation.

• Long lasting immunity to polysaccharide antigen
• T cell independent; vaccine stimulate B cells w/o assistance of T helper cells
• Prevent bacterial infection in population which polysaccharide vaccine ineffective for protection.

iv. Toxoid vaccine - Using inactivated toxin produced by bacteria (Protein based toxins (Inactivated) using heat, chemical, etc.)

• e.g. tetanus and diphtheria toxins

Vaccine Classification

v. Recombinant vaccine

• Produced by recombinant DNA technology
• Enables combination of DNA from two or more sources
• e.g. HepB, HPV, influenza vaccine - produce by inserting segment of respective viral gene into gene of yeast → modified yeast → produces pure HepB surface antigen, HIV capsid protein, influenza hemaglutinin when grows.

Types of Vaccines

Types of Vaccines

Types of Vaccines

National immunization schedule in Malaysia

GENERAL CONTRAINDICATION

Absolute contraindication for any vaccine:

Severe anaphylaxis reactions to

previous dose of the vaccine or to a

component of the vaccine.

Postponement during acute febrile illness

Minor infection without fever or

systemic upset is NOT a

contraindication.

SPECIFIC CONTRAINDICATION

1. BCG ○ Not to be given to symptomatic HIV infected children. ○ Can be given to newborns of HIV infected mother as the infant is usually asymptomatic at birth 2. Hepatitis B ○ Severe hypersensitivity to aluminium. ○ The vaccine is also not indicated for HBV carrier or immuned patient 3. Diphtheria, Tetanus (DT) ○ Severe hypersensitivity to aluminium and thiomersal 4. Pertussis ○ Anaphylaxis to previous dose; encephalopathy develops within 7 days of vaccination