<prompt> Which of the following statements is true about BCG vaccination?Distilled water is used as diluent for BCGThe site of injection should be cleaned with spiritMantoux test becomes positive after 48 hours of vaccinationWHO recommends Danish 1331 strain for vaccine production  <response>: 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: Parks Textbook of Preventive and Social Medicine 19th edition; pages 160 - 163. 