True about OPV are all, EXCEPT:

Oral polio vaccine is live attenuated vaccine containing (type 1,2,3 polio strain) It was described by Sabin in 1957,i.e. it is also known as Sabin vaccine The vaccine progeny is excreted in the faeces and secondary spread occurs to household contacts and susceptible contacts in community. Non immunized persons may therefore, be immunized. Thus wide spread 'heard immunity' results even if only 66% of community is immunized. This propey of OPV has been exploited in controlling epidemics of polio by administrating the vaccine simultaneously ina sho period to all susceptibles ina community. Live vaccine stimulates antibody formation by inducing mild infection in epithelial cell and the payers patches. Then the virus spreads to the other areas of body and produce antibody.which prevent dissemination of the virus to the nesvus tissue and paralytic polio. The presence of circulating maternal antibodies may modify the infection created by the attenuated vaccine viruses and reduce both the serum and the gut response. Production of antibodies take some time thats why we cant get quick response. Ref: Park 22nd ed/p 187.