Why can't you usually catch the same illness (like chickenpox) twice?
AThe germs die out permanently after the first infection
BYour skin becomes resistant to that specific germ
CYour immune system remembers the germ and responds faster and more effectively the second time
DAntibiotics in your body kill the germ before it can infect you again
After fighting an infection, certain white blood cells called memory cells remain in the body. If the same germ enters again, these memory cells recognize it immediately and mount a rapid, powerful response — often destroying the germ before you even feel sick. This is called immunity, and it is the principle behind vaccines.
Question 2 True / False
Fever is caused by germs attacking the body and is typically harmful.
TTrue
FFalse
Answer: False
Fever is actually an immune response — the body deliberately raises its temperature to create an environment that is harder for many germs to survive in. A moderate fever is a sign that the immune system is fighting an infection. Only very high fevers (above 104°F / 40°C) are potentially dangerous and may need medical attention.
Question 3 Short Answer
Explain how a vaccine works using the concept of immune memory.
Think about your answer, then reveal below.
Model answer: A vaccine introduces a weakened or inactive form of a germ (or a piece of it) into the body. The immune system responds by producing white blood cells that fight it and memory cells that remember it. If the real germ ever enters the body later, the memory cells recognize it and trigger a fast, strong immune response — preventing illness without the person ever getting sick.
Vaccines take advantage of the immune system's natural memory capability. By exposing the immune system to a harmless version of the germ, they allow the body to build defenses in advance, so it is prepared if the real germ appears.