Which one of the following cannot be used for preparation of vaccines against plague?

Which one of the following cannot be used for preparation of vaccines against plague?
  1. Formalin-inactivated suspensions of virulent bacteria
  2. Avirulent live bacteria
  3. Synthetic capsular polysaccharide material
  4. Heat-killed suspensions of virulent bacteria

Solution

Synthetic capsular polysaccharide vaccines are available for the treatment of pneumonia and meningitis. Vaccines against plague are prepared from the suspensions of attenuated or heat killed virulent bacteria or avirulent live bacteria.

Asked in: NEET 2010 (Mains)

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