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Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
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Which of the following statements is true about BCG vaccination?
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The correct answer is  "Danish 1331" is the strain recommended by WHO for the production of vaccine. Since the 1967, the "Danish 1331" has been in use. The quality is regularly kept in check by the International Reference Centre at Copenhagen. The diluent used in the BCG vaccine is normal saline and not distilled water. The site of injection should be cleaned with normal saline before administering the injection. The Mantoux test becomes positive after a period of 8 - 14 weeks. Ref: Park's Textbook of Preventive and Social Medicine 19th edition; pages 160 - 163.