fighting disease with disease

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Across
  1. 1. in an amount of time.
  2. 3. system something that protects and fights inside your body.
  3. 5. something that doctors inject you to prevent a virus.
  4. 9. to treat or help someone get better
  5. 10. something that's hard or difficult to do.
  6. 11. a way of doing something.
Down
  1. 1. a spreading illness that many people get sick
  2. 2. a hypothesis.
  3. 4. when you catch a virus or when your sick.
  4. 6. bacteria
  5. 7. when you catch a cold or a disease.
  6. 8. 100 years