Using kilometers in space is useless, as the distances between objects is drastically incred. A lightyear is 9.5 kilometers. It is simpler to say "Alpha Centauri is 4.1 light years away" than it is to say "Alpha Centauri is 28.95 Trillion kilometers away"<span />
A vaccine is a preparation of one or more microbial antigens to induce protective immunity in potential hosts.
Vaccines are the anti-microbial agents administered to provide immunity against specific diseases. There can be a wide variety of vaccines, like: live attenuated vaccine, vaccine with killed or inactivated microbes, vaccine containing the sub-parts of the microbes, etc.
Immunity is the body's ability fight against a disease. The immunity is build when a body gets attacked by pathogen. Various immune cells like neutrophils, MHCs, dendritic cells, B and T cells, etc. are involved in building and strengthening the immunity of any person.
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