Edward Jenner is known for developing the first vaccine for which disease?

• A. Measles
• B. Polio
• C. Rabies
• D. Smallpox

Answer: (D)

The main idea is recognizing Jenner’s contribution to the vaccination concept and which disease he targeted. Jenner showed that immunity could be created by using a milder, related virus to protect against a more dangerous one. He noticed that milkmaids who contracted cowpox, a relatively mild illness, seemed immune to smallpox. He then inoculated a healthy boy with material from a cowpox lesion, and after exposure to smallpox, the boy did not develop the disease. This demonstrated that a safer, related pathogen could train the immune system to recognize and fight a more deadly one. The disease Jenner worked on was smallpox, not measles, polio, or rabies—those vaccines were developed later by other scientists.