Invasive bacterial infections and breastfeeding
In Sweden, before general Hib immunisation was introduced, results of an ecological study3 indicated a protective effect of breastfeeding against Haemophilus influenza meningitis at a population level, and those of a case-control study showed a decreased risk for invasive H influenza infection of 5% for each added week of exclusive breastfeeding.4” Additionally, breastfeeding enhances the specific IgG2 anti-Hib response to invasive Hib infection that arises years after breastfeeding has stopped
Results. Multivariate analysis showed a significant association between invasive HI infection and two independent factors, i.e. short duration (,13 weeks) of exclusive breastfeeding, odds ratio (OR) 3.79 (95% confidence interval [CI] 1.6–8.8) and history of frequent infections, OR 4.49 (95% CI : 1.0–21.0). For the age at onset 12 months or older, the associations were stronger, OR 7.79 (95% CI : 2.4–26.6) and 5.86 (95% CI : 1.1–30.6), respectively. When breastfeeding duration in weeks was analysed as a continuous variable the OR was 0.95 (95% CI : 0.92–0.99 ), indicating a decreased risk with each additional week. Increased OR were observed for other risk factors as well but not of the magnitude found for short duration of breastfeeding.
Discussion. The association of decreased risk for invasive HI infection and long duration of breastfeeding was persisting beyond the period of breastfeeding itself. This finding supports the hypothesis of a long-lasting protective effect of breastfeeding on the risk for invasive HI infection.
The strong protective effect of breastfeeding indicates the importance of this practice for preventing invasive pneumococcal disease. The low prevalence of current breastfeeding, even among control subjects, suggests that there is ample opportunity for prevention of invasive pneumococcal disease by increased breastfeeding. The findings of this study support the American Academy of Pediatrics recommendation that all infants should be breastfed through the first year of life.16 The exact mechanisms for the impact of breastfeeding are unclear. Transfer of specific antibodies (eg, antibodies to specific pneumococcal serotypes) may play a role, but breast milk has been shown to inhibit colonization with other bacteria independent of the antibody concentration of the breast milk17 and, thus, other general bacterial inhibitors such as casein may be responsible.18