Question

Why does person previously infected with cowpox do not get infected with small pox when exposed to it?

Answer 1

because cowpox viruses does not alloe to viruses of smallpox

Answer 2

coz body has memory of first encounter with the pathogen

acctually cowpox virus is less dangerous form of small pox virus.......... so one effected with cow pox survives coz its less severe disease and the bogy gets immuned to small pox  coz body has memory of first encounter