We can be safe against diseases by vaccination.
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Disease control benefits
Unless an environmental reservoir exists, an eradicated pathogen cannot re-emerge, unless accidentally or malevolently reintroduced by humans, allowing vaccination or other preventive measures to be discontinued.
While eradication may be an ideal goal for an immunization programme, to date only smallpox has been eradicated, allowing discontinuation of routine smallpox immunization globally. Potentially, other infectious diseases with no extrahuman reservoir can be eradicated provided an effective vaccine and specific diagnostic tests are available. Eradication requires high levels of population immunity in all regions of the world over a prolonged period with adequate surveillance in place.9 The next disease targeted for eradication is polio, which is still a global challenge.10 Although high coverage with oral polio vaccine (OPV) has eliminated type 2 poliovirus globally, transmission of types 1 and 3 continues in limited areas in a few countries. OPV-caused paralytic disease, directly or by reversion to virulence, and persistent vaccine-virus excretion in immunodeficient individuals are problems yet to be solved. Global use of monovalent type 1 and type 3 OPV and inactivated polio vaccine (IPV) may eventually be required.10