BREAST feeding of infants is an almost universal feature in developing countries. In these countries it would be desirable to immunize against poliomyelitis at birth because of the high incidence of the disease in infancy1,2 and the difficulty of persuading mothers to bring back infants for immunization at a later age.
However, data for Cleveland infants reported by Lepow et al3 showed that breast feeding had an inhibitory effect on live virus vaccination. Their accumulated results have recently been published,4 as well as an experimental study demonstrating that bovine colostrum containing poliovirus antibody when fed to infants5 also inhibited live virus immunization. Holquin et al6 and Sabin et al7 have also concluded that breast feeding is detrimental to the success of oral poliovirus vaccination.
In view of these reports, we sought to determine whether immunization of breast-fed newborn infants with attenuated poliovirus would have