Mass vaccination is ineffective in inducing 'herd immunity' for:

Herd Immunity: -Reduction of infection / disease in unimmunized segment as a result of immunizing a propoion of population. - It is d/t reduced carriage of the causative microorganism by the vaccinated coho - Thus, seen only with vaccines against those diseases where humans are the only source -An effective vaccine is prerequisite for good herd effect. e.g. conjugated pneumococcal vaccine - Tetanus & BCG vaccines have no herd effect. So, mass vaccination is ineffective.