Which of the following is true about live vaccines?

Live vaccines are designed to closely mimic a natural infection, often using a weakened form of the virus or bacteria. This attribute allows them to effectively stimulate the immune system to create a robust response, leading to the development of immunity.

The statement regarding live vaccines causing mild symptoms is accurate because, while they are not supposed to cause the full-blown disease in healthy individuals, they can sometimes lead to mild, localized reactions or symptoms similar to those of a natural infection. This could include fatigue, fever, or mild rash, depending on the specific vaccine. These mild reactions are generally harmless and indicate that the body is building immunity.

This characteristic is essential for understanding how live vaccines work and why they are effective in promoting a strong immune response, often leading to long-lasting immunity after a single dose.