Question

For safety, why do vaccines use weakened or inactive parts of a pathogen instead of the full-strength version?
Because the body is unable to detect pathogens
To trigger immunity without causing illlness
Because live pathogens create a faster response
Because weakened pathogens are less expensive

Answer 1

To trigger immunity without causing illness.

Weakened (attenuated) or inactivated parts of a pathogen stimulate the immune system to build memory so the body can fight the real pathogen later, but they don’t cause the full disease the way a full-strength (virulent) pathogen would.