In vaccination, the antigens which enter the body, through injection or by mouth are harmless. The vaccine has been treated to weaken the bacteria or virus, andin som cases, dead bacteria or virus, or even extracts of the antigen substances, will cause the protective antibodies to be produced. Sometimes further vaccination or boosters are needed to provide continuing protection against the infection. To protect against tuberculosis (TB), a similar live but less dangerious baterium is used to create an infection which cause the body to develop immunity to TB. This is called inoculation, and was first used to protect against small pox, when people were injected with a milder disease called cowpox.