Protects Against Infection

a. DiarrheaChildren less than 12 months of age had a lower incidence of acute diarrheal disease during the months they were being breastfed than children that were fed with formula during the same period.
Source:  Lerman,Y. et al. "Epidemiology of acute diarrheal diseases in children in a high standard of living settlement in Israel".  Pediatr Infect Dis J 1994; 13(2);116-22.

b. Haemophilus InfluenzaIn a population based case control study of risk factors for primary invasion of haemophilus influenza, type B disease, breastfeeding was protective of infants less than 6 months of age.
Source:  Cochi, S.L. "Primary Invasive Haemophilus Influenza Type B Disease, A Population Based Assessment of Risk Factors".  Journal of Pediatrics 1986.

c. Enhances Vaccine ResponseThe antibody levels of immunized infants were significantly higher in the breastfed than the formula-fed group.  These findings are strong evidence that breastfeeding enhances the active humoral immune response in the first year of life.
Source:  Papst, H.F. , Spady, D.W.  "Effect of Breast Feeding on Antibody Response to Conjugate Vaccine".  Lancet, 1990.

The breastfed group had significantly higher antibody levels than two formula-fed groups together. Breastfed infants thus showed better serum and secretory responses to perioral and parenteral vaccines than the formula-fed, whether with a conventional or low-protein content.
Source:  Van-Coric, M.  "Antibody Responses to Parental & Oral Vaccines Where Impaired by Conventional and Low-Protein Formulas as Compared to Breast Feeding". Acta Paediatr Scand 1990; 79: 1137-42.

Human milk can transfer specific or nonspecific immunities to the external mucosal surface of the intestine and possibly to the respiratory tract of the newborn.  The acquisition of such passive immunity is particularly important in the early neonatal period when the immune system is immature.
Source:  Chang, S.J. "Antimicrobial Proteins of Maternal and Cord Sera and Human Milk in Relation to Maternal Nutritional Status". A. M. J.  CLIN NUTR, 1990.

d. NECAmong babies born at more than 30 weeks gestation, confirmed necrotizing enternal colitis was rare in those whose diet included breast milk; it was 20 times more common in those fed formula only.
Source:  Lucas, A., Cole, T.J., "Breast Milk and Neonatal Necrotizing Enteral Colitis". Lancet 1990; 336:1519-23.

e. Otitis MediaShort duration of breastfeeding involved another significant risk of recurrent respiratory infections and otitis media.
Source:  Alho, O., "Risk Factors for Recurrent Acute Otitis Media and Respiratory Infection in Infancy".  Int J Ped Otorhinolaryngology 1990; 19:151-61.

Significantly increased risk for acute otitis media as well as prolonged duration of middle ear effusion were associated with male gender, sibling history of ear infection and not being breastfed.
Source:  Teele, D.W., Apidemilogy of Otitis Media During the First Seven Years of Life in Greater Boston: A prospective, Cohort Study".  J of INFEC DIS.1989.

f. Herpes SimplexMothers milk could play a role in the protection of newborns from Herpes Simplex virus II contamination.
Source:  Lopez, I., "Neutralizing Activity Against Herpes Simplex Virus in Human Milk". Breast Feeding REV 1990; 11(2): 56-58.

g. Respiratory Syncytical Virus (RSV)Breastfeeding was associated with a lower incidence of RSV infection during the first year of life.
Source:  Holberg,C.J., "Risk Factors for RSV Associated lower Respiratory Illnesses in the First Year of Life".  AM J Epidemiol 1991; 133 (135-51).

h. Respiratory InfectionsThe authors presented results found in infants with two or more episodes of acute chronic bronchitis.  They found that approximately twice as many bottle-fed infants presented with the problem as those who were breastfed.
Source:  de Duran, C.M. "Cytologic Diagnosis of Milk Micro Aspiration".  IMM ALLERGY PRACTICE 1991; xiii (10);402-5.

There was a strong negative effect modification by breastfeeding: relative odds of respiratory illness with maternal smoking were seven times higher among children who were never breastfed then among those who were breastfed.
Source:  Woodwar, A. "Acute Respiratory Illness in Adelaide Children: Breast Feeding Modifies the Effect of Passive Smoking".  J Epidemiol in Comm Health 1990;44:224-30.