We recruited healthy infants aged 6 weeks at 42 immunisation clinics and randomly assigned them ( with blocks of 15 , three per group ) to receive a short three-dose schedule of bOPV ( bOPV short ) or mOPV1 ( mOPV1 short ) with the first dose given at age 6 weeks , the second at age 8 weeks , and the third at age 10 weeks ; or to a standard three-dose schedule of bOPV ( bOPV standard ) or mOPV1 ( mOPV1 standard ) or trivalent OPV ( tOPV standard ) with the first dose given at age 6 weeks , the second at 10 weeks , and the third at age 14 weeks .