Meningococcal vaccine refers to any of the vaccines used to prevent infection by Neisseria meningitidis.[1] Different versions are effective against some or all of the following types of meningococcus: A, B, C, W-135, and Y.[1][2] The vaccines are between 85 and 100% effective for at least two years.[1] They result in a decrease in meningitis and sepsis among populations where they are widely used.[3][4] They are given either by injection into a muscle or just under the skin.[1]