Breastfeeding after maternal immunisation during pregnancy: providing immunological protection to the newborn: a review

Epidemiological factors related to hospitalization due to influenza in children below 6 months of age

The aim of this study was to address the epidemiological factors associated to hospital admissions due to influenza in infants younger than 6 months. A case-control study was performed in a tertiary hospital in Spain. Cases were infants under 6 months of age without comorbidities who were admitted due to influenza between October 2010 and March 2015. Controls were healthy infants younger than 6 months who were hospitalized due to non-respiratory illness or non-infectious diseases (urinary tract infection was included as controls). Data were retrospectively collected from medical records and phone interviews. A total of 88 cases and 122 controls we included. From univariate analysis, differences were found in relation to maternal age (43.1 ± 4.95 vs 32 ± 5.3), paternal age (37 ± 6.4 vs 34.5 ± 6.1), having siblings (79 vs 24%), siblings below 4 years old (54 vs 15%), and having vaccinated grandparents (18 vs 39%) (p < 0.05). After logistic regression, having vaccinated grandparents was an independent protective factor (OR 0.22 [CI95%; 0.05-0.91]), while having siblings was a risk factor (OR 15.8 [CI95% 3.15-79.5]). Vaccination during pregnancy was highly uncommon (3.5 vs 8.3%; p = 0.3).

CONCLUSION

This study underlines the importance of increasing influenza immunization among household contacts of infants below 6 months to prevent their influenza admission. What is Known: • Infants younger than 6 months old are considered a high-risk population. • Vaccination against influenza is not licensed in infants below 6 months. What is New: • Increasing vaccination coverage in elderly people could reduce infants' hospitalization rates. • Cocoon immunization strategy may reduce the admission of infants.

Physiology of milk secretion

Milk is a unique and complete nutritive source for the mammal neonate, also providing immune protection and developmental signals. Lactation is a complex process, proper to the mother and child dyad, and including numerous variables ranging from psychological aspects to the secretory functioning of the mammary epithelial cells, all contributing to a successful breastfeeding. This review gives an integrated overview of the physiology of lactation with a particular focus on cellular and molecular mechanisms involved in milk product secretion and their regulations.

Maternal immunisation: collaborating with mother nature

Maternal immunisation has the potential to substantially reduce morbidity and mortality from infectious diseases after birth. The success of tetanus, influenza, and pertussis immunisation during pregnancy has led to consideration of additional maternal immunisation strategies to prevent group B streptococcus and respiratory syncytial virus infections, among others. However, many gaps in knowledge regarding the immunobiology of maternal immunisation prevent the optimal design and application of this successful public health intervention. Therefore, we did an innovative landscape analysis to identify research priorities. Key topics were delineated through review of the published literature, consultation with vaccine developers and regulatory agencies, and a collaborative workshop that gathered experts across several maternal immunisation initiatives-group B streptococcus, respiratory syncytial virus, pertussis, and influenza. Finally, a global online survey prioritised the identified knowledge gaps on the basis of expert opinion about their importance and relevance. Here we present the results of this worldwide landscape analysis and discuss the identified research gaps.

Maternal immunization: Optimizing protection for the mother and infant

Immunizing the pregnant woman to protect both the mother and her infant from infection has been utilized increasingly over the last decade. New outbreaks of pandemic influenza and the resurgence of pertussis have resulted in policy changes and shifts in health authority recommendations for a number of vaccines aimed to protect both pregnant women and their infants in the first months of life. The ability of maternal immunoglobulin IgG antibodies to be transported readily across the healthy intact placenta depends on many different factors including gestational age in the pregnancy, nature and timing of the immunization and presence of maternal HIV or malaria infections. In this paper, the history of maternal immunization is described, and specifically the studies that prompted the recommendations for tetanus, influenza, pertussis, and, when needed, meningococcus vaccines in pregnant women are reviewed. Ongoing research may result in new maternal vaccines against other pathogens including respiratory syncytial virus and group B streptococcus. Both scientific and regulatory considerations remain challenging in licensure of vaccines specifically for maternal immunization.

Quantification of vaccine-induced antipertussis toxin secretory IgA antibodies in breast milk: comparison of different vaccination strategies in women

BACKGROUND

Pertussis vaccination during pregnancy or immediately after delivery is a strategy that is increasingly being recommended to protect young infants from disease. Breast milk contains disease-specific antibodies that can contribute to the protection of young infants. The composition of breast milk could be altered by vaccination during pregnancy or near delivery. However, the quantification of these antibodies in breast milk lacks standardization.

METHODS

In this paper, sample preparation procedures and detection methods for total and antipertussis toxin (anti-PT) secretory immunoglobulin (sIg) A are proposed that can be accurately repeated and are in accordance with European Medicines Agency and Food and Drug Administration requirements. Both antibody analytes were measured in breast milk samples of lactating women obtained 8-9 weeks postpartum to compare different maternal pertussis vaccination strategies: vaccination during pregnancy, shortly after or at delivery (cocoon), less than 5 years before delivery or more than 5 years before delivery.

RESULTS

The validated immunoassays could quantitatively detect total and anti-PT sIgA in the processed breast milk samples. Significantly higher levels of anti-PT sIgA were measured in breast milk after pertussis vaccination during pregnancy or at delivery [geometric mean concentration (GMC): 2.56 and 2.15 IU/mg] in contrast to mothers with no recent (>5 years) pertussis vaccination (GMC: 0.96 IU/mg; P = 0.014 and P = 0.028).

CONCLUSION

Vaccination against pertussis in the second/third trimester of pregnancy or immediately postpartum significantly increased the levels of anti-PT sIgA in breast milk.

Pregnant women's attitudes toward influenza vaccination while breastfeeding

OBJECTIVE

The goal of this study was to assess the concerns pregnant women have about influenza vaccination while breastfeeding and to determine if having these concerns represents a barrier to vaccination uptake.

METHODS

The Vaccines and Medications in Pregnancy Surveillance System (VAMPSS) conducted a prospective cohort study in the US and Canada of influenza vaccine safety among pregnant women, oversampling vaccinated women. Data for the present paper are from an additional cross-sectional telephone survey completed during the 2010-2011 and 2012-2013 influenza seasons.

RESULTS

We surveyed 431 pregnant women about their attitudes regarding influenza vaccination while breastfeeding. Almost half of the participants identified one or two concerns and 4% reported three or more concerns. About one quarter reported that they would be unlikely to have an influenza vaccination while breastfeeding. In the multivariate model, those reporting 1-2 concerns (OR = 0.16, 95% CI 0.09-0.28) and those reported 3 or more concerns (OR = 0.07, 95% CI 0.02-0.22) had lower odds of being likely to vaccinate.

CONCLUSIONS

Pregnant women and postpartum women who are breastfeeding could benefit from receiving information and recommendations specific to vaccination from their healthcare providers, with a focus on discussing known risks and benefits to the baby's health.

The induction of breast milk pertussis specific antibodies following gestational tetanus-diphtheria-acellular pertussis vaccination

BACKGROUND

Center for Disease Control and Prevention recommends vaccination of pregnant women with tetanus-diphtheria-acellular pertussis (Tdap).

AIM

To measure pertussis specific antibodies, total protein and their ratio in breast milk following gestational Tdap vaccination.

METHODS

Women who received Tdap after the 20th week of pregnancy were recruited and unvaccinated women served as controls. Breast milk total protein, immunoglobulin A (IgA) to pertussis toxin (PT), filamentous hemagglutinin (FHA) and immunoglobulin G (IgG) to PT, FHA and pertactin (PRN) were measured. To overcome the dilution that occurs in the transition from colostrum to mature breast milk, we calculated pertussis specific antibody to total protein ratio.

RESULTS

Pertussis specific IgA was the predominant pertussis immunoglobulin in the colostrum of Tdap vaccinated women with the geometric mean concentrations (GMCs) of IgA to FHA higher than for IgA to PT, 24.12 ELISA units/milliliter (EU/mL) vs. 8.18EU/mL, respectively, p<0.004. There were differences between the vaccinated women and controls in the GMCs of IgA to FHA and IgG to PRN in the colostrum, 24.12EU/mL vs. 6.52EU/mL, p=0.01 and 2.46EU/mL vs. <0.6EU/mL, p=0.03, respectively. The GMCs of total protein showed significant decline over 8 weeks in the vaccinated women and controls, p<0.004. Among vaccinated women, there was significant decline in the GMCs of IgA to PT and FHA over 8 weeks, p<0.001. The geometric mean ratio of IgA to FHA to total protein also declined significantly over 8 weeks in the vaccinated women, p<0.01, demonstrating a true decrease, however, pertussis IgA was measurable at 8 weeks.

CONCLUSIONS

Select colostrum pertussis antibody levels were significantly higher among women vaccinated with Tdap during pregnancy compared with unvaccinated women. Among vaccinated women, maximal levels of pertussis specific IgA were in the colostrum but still detected at 8 weeks. Lactation may augment infant's protection against pertussis.