The best answer <span>to halt the growth of Communism in Europe: Nato was an equivalent of the Warsaw Pact of communist nations that promissed each other mutual defense.
Fun fact: some of the former Warsaw Pact countries are now in NATO. </span>
When the body is given weakened/dead pathogenic material this helps build up an immune system towards the actual live infection. It prepares the body for the infection so that the person does not get sick.
