OPV/ Sabin vaccine Live attenuated . Contains type 1,2 and 3 viruses grown in primary monkey kidney/human diploid cell culture. Administration:- WHO programme on immunisation (EPI) and the national immunisation program in India recommend a primary course of 3 doses of vaccine with 1 month interval commencing at 6 weeks. It is recommended that a dose of OPV is required to be given to all children delivered in the hospital before discharge. Very impoant to complete vaccination before 6 months before most cases occur between 6 months- 3 years. Dose -2 drops Immunity:- prevents paralysis and intestinal reinfection. Thus limits virus transmission in community . The vaccine progeny excreted in faeces and secondary spread occurs to household contacts and susceptible contacts in community. Non immunised persons may therefore become immunised. This propey of OPV has been exploited in controlling epidemic . Advantages:- Antibodies quickly produced and therefore helps to control epidemic. Induces both humoral and intestinal immunity. Easy to administer. Complication:- Vaccine associated paralytic polio in recipients of vaccine and their contacts . Contraindications:- Immunocompromised. Malignancy . Leukemia. Storage-Requires to be stored and transpoed at sub zero temperature,unless stabilized. Problems with OPV:- 1. Instability of vaccine at high temperatures. 2. Frequent vaccine failures. 3. Small residual neurovirulence. OPV bicalent vaccine: Contains strains types 1 and 3. {Reference: park&;s textbook of preventive and social medicine, 23rd edition, pg no.207}