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Across
  1. 1. Infectious disease caused by a virus that can cause paralysis
  2. 3. Infectious agent that can multiply in living cell
  3. 6. Enough of the population has either been vaccinated or gained immunity through natural infection to stifle the virus’s spread
  4. 7. illness
Down
  1. 2. When the body is resistant to disease
  2. 3. A substance injected to stimulate the production of antibodies
  3. 4. Contains dead or inactive
  4. 5. Chemical made by blood cells to attack pathogens