Which type of vaccines are oral typhoid and BCG classified as?

Oral typhoid and BCG (Bacillus Calmette-Guérin) vaccines are classified as live bacteria vaccines because they contain live, attenuated (weakened) forms of the bacteria that cause disease. These vaccines work by stimulating the immune system to produce a response that provides protection against future infections.

In the case of oral typhoid vaccine, it consists of live attenuated strains of Salmonella typhi which induce immunity through a natural infection process, but without causing the disease. BCG is derived from a strain of Mycobacterium bovis that has been modified and is used primarily against tuberculosis. Both vaccines rely on the principle of using live bacteria to elicit an immune response, which is why they fall under this specific classification.

The other types of vaccines mentioned, such as inactivated vaccines and subunit vaccines, do not contain live organisms but instead consist of killed pathogens or specific pieces of the bacteria (like proteins or sugars) that stimulate an immune response. Live virus vaccines involve live viruses rather than bacteria, which similarly does not apply to the vaccines in question.