How is contracting cowpox able to give immunity to smallpox?

The immune system detects invaders such as measles virus, smallpox virus, and others by molecules they have on their surfaces, called antigens. read more

Cowpox seemed to give them protection, or immunity, from smallpox. To test this idea, in 1796 Jenner took some pus from a milkmaid’s cowpox blisters and injected it into his gardener’s young son. The boy became sick but quickly recovered. read more

Jenner’s method seems irresponsible from our perspective today, but the cowpox virus did make people immune to the similar, but far more deadly, smallpox virus. Latin For Cow To distinguish his method from the riskier smallpox inoculation, Jenner named his procedure vaccination, after the Latin for cow. read more

No. The smallpox vaccine does not contain smallpox virus and cannot spread or cause smallpox. read more

After inoculation, vaccination using the cowpox virus became the primary defense against smallpox. After infection by the cowpox virus, the body (usually) gains the ability to recognize the similar smallpox virus from its antigens and is able to fight the smallpox disease much more efficiently. read more