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Some references re: breastfeeding and infectious disease


A case-control study of risk factors for Haemophilus influenzae type B disease in Navajo children.
Wolff,-M-C; Moulton,-L-H; Newcomer,-W; Reid,-R; Santosham,-M
Am-J-Trop-Med-Hyg. 1999 Feb; 60(2): 263-6
"The Hib vaccine recipients were excluded from the analyses...... Risk factors determined to be important were never breast fed (odds ratio [OR] = 3.55, 95% confidence interval [CI] = 1.52, 8.26), shared care with more than one child less than two years of age (OR = 2.32, 95% CI = 0.91, 5.96); wood heating (OR = 2.14, 95% CI = 0.91, 5.05); rodents in the home (OR = 8.18, 95% CI = 0.83, 80.7); and any livestock near the home (OR = 2.18, 95% CI = 0.94, 5.04).”

Protective effect of breastfeeding: an ecologic study of Haemophilus influenzae meningitis and breastfeeding in a Swedish population.
Silfverdal,-S-A; Bodin,-L; Olcen,-P
Int-J-Epidemiol. 1999 Feb; 28(1): 152-6
"CONCLUSION: There seems to be an association between high breastfeeding rate in the population and a reduced incidence of HI meningitis 5 to 10 years later. These results do have implications on strategies for breastfeeding promotion, especially in countries where Hib vaccination is too costly and not yet implemented."


Incidence of Haemophilus influenzae in the throats of healthy infants with different feeding methods.
Hokama,-T; Sakamoto,-R; Yara,-A; Asato,-Y; Takamine,-F; Itokazu,-K
Pediatr-Int. 1999 Jun; 41(3): 277-80
"Haemophilus influenzae is the major cause of otitis media and lower respiratory tract infection in childhood. In the presence of human milk, which contains numerous host defense factors, Haemophilus influenzae may be inhibited in attaching to and colonizing pharyngeal cells. We investigated the incidence of H. influenzae in the throats of 162 healthy infants with different feeding methods: 70 breast-fed, 49 mixed-fed and 43 formula-fed infants. METHODS AND RESULTS: Haemophilus influenzae was identified using standard microbiological procedures and the API NH system. The incidence of H. influenzae in breast-fed infants, mixed-fed infants and formula-fed infants was 0, 0 and 7.0% respectively. CONCLUSION: The results suggest that the colonization of H. influenzae in the throat was inhibited by the presence of breast milk."


Isolation of respiratory bacterial pathogens from the throats of healthy infants fed by different methods.
Hokama,-T; Yara,-A; Hirayama,-K; Takamine,-F
J-Trop-Pediatr. 1999 Jun; 45(3): 173-6
"We investigated the incidence of pathogenic bacteria isolated from the throat of healthy infants with different feeding methods. The protecting role of breastmilk is also discussed. The incidence of respiratory bacterial pathogens isolated from the oropharynx of 113 normal infants with different feeding methods was investigated. Group A beta haemolytic Streptococcus, Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis were selected as respiratory bacterial pathogens. No respiratory bacterial pathogens were detected in breastfed and mixed-fed infants. Haemophilus influenzae and Moraxella catarrhalis were isolated from the oropharynx of formula-fed infants. The incidence of respiratory bacterial pathogens did differ among infants with different feeding methods. These results suggest that breastmilk may inhibit the colonization by respiratory bacterial pathogens of the throat of infants, by enhancing mucosal immunity against respiratory tract infection."


Human milk and host defence: immediate and long-term effects.

Acta-Paediatr-Suppl. 1999 Aug; 88(430): 42-6
"Convincing studies demonstrate significant protection during breastfeeding against diarrhoea, respiratory tract infections, otitis media, bacteraemia, bacterial meningitis, botulism, urinary tract infections and necrotizing enterocolitis. There is also good evidence for enhanced protection for years after the termination of breastfeeding against Haemophilus influenzae type b infections, otitis media, diarrhoea, respiratory tract infections and wheezing bronchitis. In some reports breastfeeding has also improved vaccine responses. Several studies show that milk may actively stimulate the immune system of the offspring via transfer of anti-idiotypic antibodies and lymphocytes. This may explain why breastfeeding diminishes the risk of developing coeliac disease. Some investigations suggest that there may also be a similar effect on allergic diseases and autoimmune diseases, as well as inflammatory bowel diseases and certain tumours. This needs to be confirmed."


Dietary nucleotides: effects on the immune and gastrointestinal systems.
Acta-Paediatr-Suppl. 1999 Aug; 88(430): 83-8
"Nucleotides (NT) and their related metabolic products play key roles in many biological processes.......Animals fed NT-supplemented versus non-NT supplemented diets have enhanced gastrointestinal growth and maturation, and improved recovery following small and large bowel injury. Indices of humoral and cellular immunity are enhanced, and survival rates are higher following infection with pathogens. Infants receive NT in human milk, where they are present as nucleic acids, nucleosides, nucleotides and related metabolic products. The NT content of human milk is significantly higher than most cow's milk-based infant formulae. Dietary NT are reported to enhance the gastrointestinal and immune systems of formula-fed infants. Infants fed NT-supplemented versus non-supplemented formula have a lower incidence of diarrhea, higher antibody titers following Haemophilus influenzae type b vaccination and higher natural killer cell activity. These data suggest that human milk NT may contribute to the superior clinical performance of the breastfed infant."


Modulation of the immune system by human milk and infant formula containing nucleotides.
Pickering,-L-K; Granoff,-D-M; Erickson,-J-R; Masor,-M-L; Cordle,-C-T; Schaller,-J-P; Winship,-T-R; Paule,-C-L; Hilty,-M-D
Pediatrics. 1998 Feb; 101(2): 242-9
"OBJECTIVE: To determine whether human milk and nucleotides added to infant formula at levels present in human milk enhance development of the immune system during infancy........  OUTCOME VARIABLES: Antibody responses were determined at 6, 7, and 12 months of age to Haemophilus influenzae type b polysaccharide (Hib), to diphtheria and tetanus toxoids, and to oral polio virus (OPV) immunizations. RESULTS: Of 370 full-term, healthy infants enrolled, 311 completed the study (107 Control, 101 Nucleotide, 103 human milk/Similac with iron). Intake, tolerance, and growth of infants were similar in all three groups. Compared with the Control group 1 month after the third immunization (7 months of age), the Nucleotide group had a significantly higher Hib antibody concentration (geometric mean concentrations of 7.24 vs 4.05 micrograms/mL, respectively), and a significantly higher diphtheria antibody concentration (geometric mean of 1.77 vs 1.38 U/mL). The significantly higher Hib antibody response in the Nucleotide group persisted at 12 months. The antibody responses to tetanus and OPV were not enhanced by nucleotide fortification. There also was an effect of breastfeeding on immune response. Infants who breastfed had significantly higher neutralizing antibody titers to polio virus than either formula-fed group (1:346 vs 1:169 and 1:192 in the Control and Nucleotide groups, respectively) at 6 months of age. CONCLUSION: Infant formula fortified with nucleotides enhanced H influenzae type b and diphtheria humoral antibody responses. Feeding human milk enhanced antibody responses to OPV. Dietary factors play a role in the antibody response of infants to immunization."


The epidemiology of Haemophilus influenzae type b carriage among infants and young children in Santo Domingo, Dominican Republic.
Gomez,-E; Moore,-A; Sanchez,-J; Kool,-J; Castellanos,-P-L; Feris,-J-M; Kolczak,-M; Levine,-O-S
Pediatr-Infect-Dis-J. 1998 Sep; 17(9): 782-6
"BACKGROUND: Whether herd immunity will occur with widespread Haemophilus influenzae type b (Hib) vaccination in developing countries is dependent on whether the vaccines are capable of reducing carriage in these settings.... Hib carriage was 51% lower among currently breast-fed 6 to 11 month olds than among those not currently breast-fed (18.2% vs. 9.0%; P=0.08). CONCLUSIONS: Infants and young children in Santo Domingo have high rates of Hib carriage, characterized by an early peak in carriage that corresponds with the peak of risk for Hib meningitis. The ability of Hib vaccines to diminish carriage to levels that will effectively reduce transmission and lead to herd immunity in this setting needs to be determined."


Breastfeeding provides passive and likely long-lasting active immunity.
Ann-Allergy-Asthma-Immunol. 1998 Dec; 81(6): 523-33; quiz 533-4, 537
"OBJECTIVES: The reader of this review will learn about the mechanisms through which breastfeeding protects against infections during and most likely after lactation, as well as possibly against certain immunologic diseases, including allergy. .....RESULTS: Human milk protects against infections in the breastfed offspring mainly via the secretory IgA antibodies, but also most likely via several other factors like the bactericidal lactoferrin. It is striking that the defense factors of human milk function without causing inflammation, some components are even directly anti-inflammatory. Protection against infections has been well evidenced during lactation against, e.g., acute and prolonged diarrhea, respiratory tract infections, otitis media, urinary tract infection, neonatal septicemia, and necrotizing enterocolitis. There is also interesting evidence for an enhanced protection remaining for years after lactation against diarrhea, respiratory tract infections, otitis media, Haemophilus influenzae type b infections, and wheezing illness. In several instances the protection seems to improve with the duration of breastfeeding. Some, but not all studies have shown better vaccine responses among breastfed than non-breastfed infants. A few factors in milk like anti-antibodies (anti-idiotypic antibodies) and T and B lymphocytes have in some experimental models been able to transfer priming of the breastfed offspring. This together with transfer of numerous cytokines and growth factors via milk may add to an active stimulation of the infant's immune system. Consequently, the infant might respond better to both infections and vaccines. Such an enhanced function could also explain why breastfeeding may protect against immunologic diseases like coeliac disease and possibly allergy. Suggestions of protection against autoimmune diseases and tumors have also been published, but need confirmation. CONCLUSIONS: Breastfeeding may, in addition to the well-known passive protection against infections during lactation, have a unique capacity to stimulate the immune system of the offspring possibly with several long-term positive effects."


Protective effect of breastfeeding on invasive Haemophilus influenzae infection: a case-control study in Swedish preschool children.
Silfverdal,-S-A; Bodin,-L; Hugosson,-S; Garpenholt,-O; Werner,-B; Esbjorner,-E; Lindquist,-B; Olcen,-P
Int-J-Epidemiol. 1997 Apr; 26(2): 443-50
"BACKGROUND: In Orebro County a 2.5-fold increase in the incidence of Haemophilus influenzae (HI) meningitis was found between 1970 and 1980, an observation that initiated the present study..... 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. CONCLUSION: A decreased risk for invasive HI infection with long duration of breastfeeding was found. Our results do have implications for strategies in breastfeeding promotion, especially in countries where Hib vaccination is too costly and not yet implemented."


Does breast feeding protect against non-gastric infections?
Golding,-J; Emmett,-P-M; Rogers,-I-S
Early-Hum-Dev. 1997 Oct 29; 49 SupplS105-20
"There is convincing evidence that breast-feeding is protective against gastro-enteritis and diarrhoea, but for other infections the situation is less clear cut. There is evidence that breast-fed infants are at increased risk of one infection (infant botulism). They are probably not significantly protected from upper respiratory tract infections (other than otitis media.), but they may be at a decreased risk of lower respiratory tract infections, particularly those associated with respiratory syncytial virus. There is strong evidence that Haemophilus influenzae B infection is more likely in the bottle-fed infant, and consistent evidence of protection of young children from chronic otitis media with prolonged breast-feeding."


Human milk secretory IgA antibody to nontypeable Haemophilus influenzae: possible protective effects against nasopharyngeal colonization.
Harabuchi,-Y; Faden,-H; Yamanaka,-N; Duffy,-L; Wolf,-J; Krystofik,-D
J-Pediatr. 1994 Feb; 124(2): 193-8
"Prevention of colonization was most evident during breast-feeding. These data suggest that the protective effects of human milk against otitis media may be due in part to inhibition of nasopharyngeal colonization with nontypeable H. influenzae by specific secretory IgA antibody."


A prospective cohort study on breast-feeding and otitis media in Swedish infants.
Aniansson,-G; Alm,-B; Andersson,-B; Hakansson,-A; Larsson,-P; Nylen,-O; Peterson,-H; Rigner,-P; Svanborg,-M; Sabharwal,-H; et-al.
Pediatr-Infect-Dis-J. 1994 Mar; 13(3): 183-8
"The AOM (acute otitis media) frequency was significantly lower in the breast-fed than in the non-breast-fed children in each age group (P < 0.05). The first AOM episode occurred significantly earlier in children who were weaned before 6 months of age than in the remaining groups. The frequency of nasopharyngeal cultures positive for Haemophilus influenzae, Moraxella catarrhalis and Streptococcus pneumoniae was significantly higher in children with AOM. At 4 to 7 and 8 to 12 months of age, the AOM frequency was significantly higher in children with day-care contact and siblings (P < 0.05 and < 0.01, respectively). The frequency of upper respiratory tract infections was increased in children with AOM but significantly reduced in the breast-fed group."


Preventing otitis media.
Ann-Otol-Rhinol-Laryngol-Suppl. 1994 May; 16320-3
"Recurrent acute otitis media (AOM) is an extremely prevalent disease in young children. Epidemiologic associations suggest that primary prevention or reduction of AOM frequency may be achieved with breast-feeding during infancy, elimination of household tobacco smoking, and use of small rather than large day-care arrangements for infants and toddlers. Secondary antimicrobial prophylaxis with amoxicillin or sulfisoxazole reduces the frequency of recurrent AOM by about 50%, but it does not appear to reduce the duration of otitis media with effusion (OME). Tympanostomy tube insertion is not as effective as amoxicillin in reducing AOM frequency in children without OME. Adenoidectomy appears to be warranted for children who develop recurrent AOM after extrusion of tubes. Vaccines against the common bacteria and viruses causing AOM hold the greatest promise of preventing AOM and blocking the sequence of pathologic events leading to chronic OME and middle ear sequelae. The greatest progress has been made recently with pneumococcal protein conjugate vaccines, and clinical testing is in progress."
Gee, I wonder why vaccines hold the greatest promise when breasfeeding prevents or reduces AOM frequency?


Immunogenicity of Haemophilus influenzae type b tetanus toxoid conjugate vaccine in young infants. The Kaiser-UCLA Vaccine Study Group.
Greenberg,-D-P; Vadheim,-C-M; Partridge,-S; Chang,-S-J; Chiu,-C-Y; Ward,-J-I
J-Infect-Dis. 1994 Jul; 170(1): 76-81
In a prospective, randomized, double-blind efficacy trial, the immunogenicity of 10 lots of Haemophilus influenzae type b capsular polysaccharide-tetanus toxoid conjugate vaccine (PRP-T) was evaluated. More than 10,000 infants received PRP-T or hepatitis B vaccine at about 2, 4, and 6 months of age along with other childhood vaccines. Oh, where oh where could the never vaccinated be? .........In a stepwise regression model, the most important additional factors affecting anticapsular antibody concentrations were the time between the third dose and the blood draw, race, and breast-feeding status at 6 months of age."


Breast feeding: overview and breast milk immunology.
Hanson,-L-A; Hahn-Zoric,-M; Berndes,-M; Ashraf,-R; Herias,-V; Jalil,-F; Bhutta,-T-I; Laeeq,-A; Mattsby-Baltzer,-I
Acta-Paediatr-Jpn. 1994 Oct; 36(5): 557-61
"Thus the adherence of Haemophilus influenzae and pneumococci for example to retropharyngeal cells is efficiently inhibited by
human milk. This may be one explanation for the fact that breast-fed babies have less otitis media than the non-breast-fed. Other milk factors like lysozyme and lactoferin may contribute to the host defence, but this has not yet been well defined. However, human milk also supports the well-being of the infant by being anti-inflammatory


Day care attendance and other risk factors for invasive Haemophilus influenzae type b disease.
Arnold,-C; Makintube,-S; Istre,-G-R
Am-J-Epidemiol. 1993 Sep 1; 138(5): 333-40
"Two hundred and ninety-five of 373 (79%) children with reported cases of invasive Haemophilus influenzae type b (Hib) occurring in the state of Oklahoma from January 1, 1986, through December 31, 1987, were matched according to birth date with two controls each. Conditional logistic regression was used to assess the independent roles of day care attendance, number of young children in the home, crowding, passive smoking, maternal education, household income, and race in Hib disease. Statistically significant odds ratios (ORs) were found for day care attendance (OR = 2.9), the presence of two or more children in the home under 6 years of age (OR = 2.4), crowding (ratio of number of people in the home to number of bedrooms > or = 2) (OR = 2.0), and exposure to cigarette smoking in the home (OR = 1.4). Household income was independently associated with Hib disease. African Americans were at increased risk even after adjustment for income and crowding (OR = 4.1). Although there were no important differences in risk for other factors by type of Hib disease, there was a large and statistically significant difference in risk for day care attendance between meningitis (adjusted OR = 5.1, 95% confidence interval (CI) 3.1-8.2) and other types of Hib disease (combining nonmeningitis cases, adjusted OR = 1.6, 95% CI 0.9-2.7). Increasing numbers of hours per week of day care attendance and children per room were associated with increasing risk of Hib meningitis in a dose-response pattern. The highest day care ORs for meningitis were observed in the youngest (< 6 months) and oldest (> or = 24 months) children. The adjusted OR for exposure to
breast feeding was 0.5 (95% CI 0.3-0.8). A protective effect for Hib polysaccharide vaccination among children aged > or = 18 months was suggested but did not reach statistical significance (OR = 0.4, 95% CI 0.2-1.1)."


Prevalence of bacterial respiratory pathogens in the nasopharynx in breast-fed versus formula-fed infants.
Kaleida,-P-H; Nativio,-D-G; Chao,-H-P; Cowden,-S-N
J-Clin-Microbiol. 1993 Oct; 31(10): 2674-8
"In several studies, breast-feeding has been associated with decreased frequency or duration of otitis media episodes. If a causal relationship exists, the mechanism of protection of breast-feeding has not been established. We hypothesized that infants who are
breast-fed, compared with infants who are formula-fed, have a lower prevalence of nasopharyngeal colonization with the bacterial respiratory pathogens (Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, Streptococcus pyogenes) commonly isolated from the middle ear effusions of children with acute otitis media. In two private pediatric practices, we obtained specimens from the nasopharynx for culture from 211 infants at 1 month of age and from 173 of these infants at 2 months of age. A swab was left in place in the nasopharynx for 45 s and was then immediately transferred onto appropriate culture media. Exclusively breast-fed (n = 84) and exclusively formula-fed (n = 76) infants were similar regarding the number of persons in the household, the number of children in the household, the number of siblings in day care, and the proportion with a recent upper respiratory tract infection. The two groups did not differ significantly in the proportions found to have one or more respiratory pathogens at 1 month of age (10.7 versus 18.4%; P = 0.12) or 2 months of age (34.8 versus 35.1%; P = 0.57). We conclude that during the first 2 months after birth, the exclusive receipt of breast milk appears not to substantially influence the prevalence of nasopharyngeal colonization with common bacterial respiratory pathogens."

Maybe this isn't the right question. Perhaps colonization alone does not tell the whole story.  Perhaps it is the ability to effectively respond to such colonization that matters.


Risk factors for invasive Haemophilus influenzae type b in Los Angeles County children 18-60 months of age.
Vadheim,-C-M; Greenberg,-D-P; Bordenave,-N; Ziontz,-L; Christenson,-P; Waterman,-S-H; Ward,-J-I
Am-J-Epidemiol. 1992 Jul 15; 136(2): 221-35
"We conclude that exposure to smoking in the home, living in households with more than six members, and the black race are each independently associated with an increased risk for H. influenzae type b disease in Los Angeles County children and, when combined, constitute a major reason for H. influenzae type b disease occurrence."


Epidemiology of acute respiratory infections in children of developing countries.
Rev-Infect-Dis. 1991 May-Jun; 13 Suppl 6S454-62
"Acute respiratory infections cause four and a half million deaths among children every year, the overwhelming majority occurring in developing countries. Pneumonia unassociated with measles causes 70% of these deaths; post-measles pneumonia, 15%; pertussis, 10%; and bronchiolitis and croup syndromes, 5%. Both bacterial and viral pathogens are responsible for these deaths. The most important bacterial agents are Streptococcus pneumoniae, Haemophilus influenzae, and Staphylococcus aureus. The data on bacterial etiology of pneumonia during the first 3 months of life are limited, and almost no information on the role of chlamydia and pertussis in this age period is available. The distribution of viral pathogens in developing countries can be summarized as follows: respiratory syncytial virus, 15%-20%; parainfluenza viruses, 7%-10%; and influenza A and B viruses and adenovirus, 2%-4%. Mixed viral and bacterial infections occur frequently. Risk factors that increase the incidence and severity of lower respiratory infection in developing countries include large family size, lateness in the birth order, crowding, low birth weight, malnutrition, vitamin A deficiency, lack of
breast feeding, pollution, and young age. Effective interventions for prevention and medical case management are urgently needed to save the lives of many children predisposed to severe disease."


Effects of age, breast feeding, and household structure on Haemophilus influenzae type b disease risk and antibody acquisition in Alaskan Eskimos.
Petersen,-G-M; Silimperi,-D-R; Chiu,-C-Y; Ward,-J-I
Am-J-Epidemiol. 1991 Nov 15; 134(10): 1212-21
"The authors found that
breast feeding was significantly less common among cases than controls (p less than 0.03; odds ratio = 0.53; 95% confidence interval 0.27-0.98). Although there was a positive correlation between age and acquired level of total anticapsular antibody (r = 0.59; p less than 0.0001), previous exposure to invasive Hib disease did not influence these levels. Household crowding and breast feeding also did not appear to affect Hib antibody acquisition."

Without reading this article, I can't be sure of the significance of the last sentence.


Selective concentration of IgD class-specific antibodies in human milk.
Litwin,-S-D; Zehr,-B-D; Insel,-R-A
Clin-Exp-Immunol. 1990 May; 80(2): 263-7
"In the group of unimmunized women, although selective concentration of total IgD was observed, specific antibody studies were inconclusive due to the low milk IgD antibody levels encountered. The results indicate that IgD (and also IgM) may participate in local immune responses
of human breast tissues and fluids; possibly influenced by the nature of the antigen, the state of immunization and the hormonal environment (pregnancy)."


Anti-adhesive activity of human casein against Streptococcus pneumoniae and Haemophilus influenzae.
Aniansson,-G; Andersson,-B; Lindstedt,-R; Svanborg,-C
Microb-Pathog. 1990 May; 8(5): 315-23
"The casein fraction of human milk was found to inhibit the attachment of Streptococcus pneumoniae and Haemophilus influenzae human respiratory tract epithelial cells........ This anti-microbial effect of human casein represents a new mechanism for the protection by breast-milk against respiratory tract infection."

Effect of breast-feeding on antibody response to conjugate vaccine.
Pabst,-H-F; Spady,-D-W
Lancet. 1990 Aug 4; 336(8710): 269-70
Infants were immunised at the ages of 2, 4, and 6 months with conjugate Haemophilus influenzae type b vaccine, and their responses to the vaccine were evaluated by feeding method (breast or formula). There were no significant differences between the groups in antibody levels at early ages. However the antibody levels were significantly higher in the breast-fed (57 infants) than the formula-fed group (24 infants) at 7 months (mean [SD] 29.8 [32.0] vs 17.5 [14.8] micrograms/ml) and at 12 months (55 vs 26 infants; 4.8 [4.4] vs 3.0 [2.3] micrograms/ml). These findings are strong evidence that breast-feeding enhances the active immune response in the first year of life, and therefore the feeding method must be taken into account in the evaluation of vaccine studies in infants."  How ironic.

Risk factors of invasive Haemophilus influenzae type b disease among children in Finland.
Takala,-A-K; Eskola,-J; Palmgren,-J; Ronnberg,-P-R; Kela,-E; Rekola,-P; Makela,-P-H
J-Pediatr. 1989 Nov; 115(5 Pt 1): 694-701
"In the multivariate analysis, day care outside the home was found to increase the risk of invasive Hib disease (odds ratio 5, 95% confidence interval 2.3 to 11), with the highest risk among children less than 2 years of age; this risk was significantly higher within the first month of attendance than later on (p = 0.02). The existence of siblings less than 7 years of age was found to be a risk factor, especially for the younger children (odds ratio 8.6, 95% confidence interval 2.6 to 52 for children less than 1 year of age), and the odds ratio increased approximately twofold with each additional sibling. A history of otitis media and previous hospitalizations were further risk factors for invasive Hib disease (odds ratio 2.2, 95% confidence interval 1.2 to 3.9, and odds ratio 1.9, 95% confidence interval 1.0 to 3.4, respectively). Breast-feeding for longer than 6 months was found to be protective (odds ratio 0.47, 95% confidence interval 0.3 to 0.9). The amount of Hib disease in different populations will vary with the incidence of these risk factors."

Class-specific antibodies to Bordetella pertussis, Haemophilus influenzae type b, Streptococcus pneumoniae and Neisseria meningitidis in human breast-milk and maternal-infant sera.
Kassim,-O-O; Raphael,-D-H; Ako-Nai,-A-K; Taiwo,-O; Torimiro,-S-E; Afolabi,-O-O
Ann-Trop-Paediatr. 1989 Dec; 9(4): 226-32
"Children under 2 years of age are most susceptible to acute respiratory infections caused by Bordetella pertussis, Haemophilus influenzae type b, Streptococcus pneumoniae and Neisseria meningitidis. We analysed milk samples and sera from mother-infant pairs for specific antibodies that may enhance protection against the bacterial pathogens. The results show that the breast-milk samples contained significant titres of specific IgG and IgA antibodies to the four organisms, although the mean IgG antibody levels were higher in maternal sera than in breast-milk. On the other hand, the mean IgA antibody levels to the four organisms were higher in breast-milk than in both maternal and infant sera. IgM antibodies to these organisms were relatively low or absent in many milk and serum samples. Nevertheless, the significant concentrations of specific IgG and IgA antibodies in milk samples may indicate a protective role for breast-milk against the four infections in early childhood."  Even whooping cough.

Day-care center attendance and hospitalization for lower respiratory tract illness.
Anderson,-L-J; Parker,-R-A; Strikas,-R-A; Farrar,-J-A; Gangarosa,-E-J; Keyserling,-H-L; Sikes,-R-K
Pediatrics. 1988 Sep; 82(3): 300-8
"A parent or guardian for each patient and control was interviewed by telephone regarding demographic data, care outside the home, breast-feeding, previous medical history, allergies, and smoking and illness in household members. Five factors were associated with lower respiratory tract illness in both a univariate analysis and a multiple logistic regression model (P less than .05). These factors were the number of people sleeping in the same room with the child, a lack of immunization the month before the patient was hospitalized, prematurity, a history of allergy, and regular attendance in a day-care center (more than six children in attendance). Care received outside of the home in a day-care home (less than or equal to six children in attendance) was not associated with lower respiratory tract illness. The suggestion made by our study and other studies was that for children less than 2 years of age, care outside of the home is an important risk factor for acquiring lower respiratory tract illness, as well as other infectious diseases, and that this risk can be reduced by using a day-care home instead of a day-care center."  This study was one of the few which did not identify breastfeeding as protective. 

Primary invasive Haemophilus influenzae type b disease: a population-based assessment of risk factors.
Cochi,-S-L; Fleming,-D-W; Hightower,-A-W; Limpakarnjanarat,-K; Facklam,-R-R; Smith,-J-D; Sikes,-R-K; Broome,-C-V
J-Pediatr. 1986 Jun; 108(6): 887-96
"Fifty percent of all invasive Hib disease that occurred during the study period was attributable to exposure to day-care; the attributable risk for household crowding was 18%. Dose-response effects were observed for hours per week of day-care attendance and extent of household crowding. Breast-feeding was protective for infants less than 6 months of age (OR 0.08, 95% CL 0.01 to 0.59). After controlling for socioeconomic and other confounding factors, we could demonstrate no effect of black race on cumulative risk of invasive Hib disease. Our study defines high-risk groups and provides a population-based model of the interrelationship between risk factors associated with invasive Hib disease."

Risk factors for primary invasive Haemophilus influenzae disease: increased risk from day care attendance and school-aged household members.
Istre,-G-R; Conner,-J-S; Broome,-C-V; Hightower,-A; Hopkins,-R-S
J-Pediatr. 1985 Feb; 106(2): 190-5
"Infected children were more likely to have attended a day care center or nursery (DCC/N) and to have an elementary school-aged household member. For attendance at DCC/N, the relative risk was significantly increased only for children 12 months of age or older, and increased with the size of the DCC/N. After controlling for DCC/N attendance and school-aged siblings, children younger than 6 months of age with infection were significantly less likely to have been breast-fed, suggesting a protective effect of breast-feeding. We identified DCC/N attendees, especially those older than 1 year of age, to be at increased risk of primary H. influenzae disease. They could benefit from immunization."  Don't know why breastfed children, older than 6 months old in this study, not identified as at decreased risk.  Others indicate the longer you breastfeed the better.
I guess the first question has to be, who paid for the study......?

Breast milk antibody to the capsular polysaccharide of Haemophilus influenzae type b.
Pichichero,-M-E; Sommerfelt,-A-E; Steinhoff,-M-C; Insel,-R-A
J-Infect-Dis. 1980 Nov; 142(5): 694-8
"Breast milk has a high concentration of secretory immunoglobulin and potentially could serve as a source of passive antibody protection of infants against systemic invasion by Haemophilus influenzae type b. Specific antibody to the capsular polysaccharide of this organism was detected in the colostrum and all subsequent milk samples in 11 of 12 women with a radioactive antigen binding assay. The geometric mean concentrations of antibody were 1.99 microgram/ml in colostrum and 0.18 microgram/ml in breast milk at six weeks and after four and one-half to six months of lactation. Antibody levels in colostrum correlated positively with those in subsequent milk samples; levels after six weeks of lactation correlated highly with those present after four and one-half to six months of lactation. IgA was the predominant immunoglobulin class of anticapsular antibody in the colostrum and milk samples as detected by an enzyme-linked immunosorbent assay."