Effect of immunization against rubella on lactation products. II. Maternal-neonatal interactions.

The transmission of rubella virus to newborn infants via the process of breast-feeding was studied after immunization of 16 breast-feeding and 10 non-breast-feeding mothers with HPV-77 DE5 live, attenuated rubella virus vaccine administered subcutaneously or RA 27/3 live, attenuated rubella virus vaccine administered intranasally or subcutaneously in the immediate postpartum period. Infectious rubella virus or virus antigen was observed in the breast milk of 11 (68%) of the 16 vaccinated, breast-feeding women studied. After maternal immunization, infectious rubella virus or virus antigen was recovered from the nasopharynx and throat of 56% of the breast-fed infants and from none of the non-breast-fed infants. Of the breast-fed infants, 25% showed transient seroconversion to rubella virus but without any clinical disease. No rubella virus-specific seroconversion was observed in the non-breast-fed infants. These observations provide strong support for the communicability of rubella virus to neonates via the process of breast-feeding.