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