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BCG Vaccine

Bacillus Calmette Guerin

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• BCG vaccine protects against Tuberculosis.

• This is a suspension of living cells of a strain of Mycobacterium tuberculosis known as the bacillus of Calmette & Guerin.

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Calmette & Guerin were French bacteriologists.They investigated attenuated Vaccines.

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• A bovine (cattle) strain was selected in the hope that it would be safer for man than the human variety.

• It was grown on a medium containing ox bile as this had been found to reduce virulence of organisms in culture in which it had been used to break up clumps of cells.

• It was sub-cultured on this medium for 13 years, by which time it had become safer to administer to human & was stable.

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• BCG should be given as early as possible in life, before child comes in contact with tuberculosis.

• It can be given up to 5 years of age.• BCG vaccination is rarely given to anyone over

the age of 16 - and never over the age of 35, because it doesn't work very well in adults.

• It is, however, given to adults aged between 16 and 35 who are at risk of TB through their work, such as some healthcare.

• The vaccine is 70-80% effective against the most severe forms of TB.

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Route of AdministrationIntracutaneous

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• This kind of characteristic lesion (scar) is formed at the site of Injection, but it remains localized.

• This demonstrates living nature of the cell.

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• Formation of scar is neither necessary nor is the only indication of success of BCG vaccine.

• However it is the only simple & convenient way of determining success of BCG vaccine.

• It may take 3-6 months for the scar to form. • If no scar is visible at all after 6 months one

needs to do Mantoux test. • If negative, one should give repeat BCG.

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Preparation• A factor that makes a great impact on the

preparation & testing of attenuated vaccines is the importance of preventing & detecting contamination of product with virulent strains.

• Strict regulations are laid down for the manufacture of this kind of preparation.

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This includes:- • Use of a completely self-contained laboratory

suite in which no living organisms except the BCG strain are allowed,

• Superlative air-conditioning, • Regular X-ray examinations of staff .To prevent contamination with virulent human

tubercle bacilli.

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• The methods used to prepare dead & living bacterial vaccines are essentially the same except that for living preparations-

I. There is no sterilization stage,II. The viability of the cells must be maintained,III. Standardization is on the basis of a viable

count.

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Before Use, the strain is rigorously checked for antigenicity and freedom from pathogenicity.

It is than grown on a liquid medium for not more than 14 days, older cultures being less efficient antigens.

Then the organisms are seperated by centrifugation, washed & suspended in a vehicle that preserves antigenicity & viability for as long as possible.

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• The resulting liquid vaccine has been replaced by a freeze-dried form because the former has serious disadvantages-

1. Even when stored under ideal conditions(2 to 10° C & protected from light) it rapidly deteriorates, due to loss of viability, & is unfit for use after 14 days from harvesting.

2. Because of its short life, control tests including the vital test for virulence (which takes 6 weeks to complete) can not be finished until after the vaccine has been issued for use.

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• The freeze dried preparation, when stored under the same conditions as the liquid form, retains its potency for at least a year and, therefore all the test can & must be completed before use.

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• The application of freeze drying to vaccines presents a number of difficulties-

a) The product may be unsightly that is pharmaceutically unacceptable.

b) The material may be so fluffy that part of the contents is lost when the vacuum is released in the drying chamber.

c) It may be very difficult to obtain a clump free homogenous suspension when the vaccine is reconstituted with sterile saline or water.

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Ingredients used in growth medium

Name PurposeNon-ionic surfactant (polyoxy ethylene ether)

BCG tends to clump badly when grown in conventional liquid media, Use of this non ionic surfactant eliminates clumping problem.Improves appearance of product.

Dextran Reduce fluffiness Assist reconstitution.

Glucose Prevents excessive drying.In the correct concentration, allows retention of the optimum amount of moisture.

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Marketed Product

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• COMPOSITION• Each 1ml contains between :

1 x106 and 33 x 106 Colony Forming Units (C.F.U.)

• Diluent :Sodium Chloride Injection I.P. • Dose : 0.05 ml for children under one month

of age & 0.1 ml for children over one month of age and adults.

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Thank You