<prompt> Which vaccine gives herd immunity-OPVTyphoidCholeraNone  <response>: Ans. is a i.e., OPV o The vaccine progeny of OPV is excreted in the faeces and secondary spread occurs to household contacts and susceptible contacts in the community. o Non-immunized persons may therefore, be immunized. o Thus widspread herd immunityresults, even if only approximately 66 of the community is immunized. 