Protective effect of exclusive breastfeeding and effectiveness of maternal vaccination in reducing pertussis-like illness

Pertussis in Early Infancy: Diagnostic Challenges, Disease Burden, and Public Health Implications Amidst the 2024 Resurgence, with Emphasis on Maternal Vaccination Strategies

Bordetella pertussis is the causative agent of pertussis or whooping cough, an acute and highly contagious respiratory infection that can have serious and fatal complications such as pneumonia, encephalopathy, and seizures, especially for newborns. The disease is endemic not only in the European Union (EU)/European Economic Area (EEA) but also globally. Larger outbreaks are anticipated every three to five years, even in countries where vaccination rates are high. Despite the high pertussis vaccination coverage in developed countries and a low rate of pertussis incidence for many years, especially during the COVID-19 pandemic, the incidence of pertussis has been on the rise again, with outbreaks in some places, which is referred to as "re-emergence of pertussis". The aim of this review is to underscore the critical importance of achieving high vaccination coverage, particularly among pregnant women, to safeguard vulnerable neonates from pertussis during their early months, before they are eligible for vaccination. This aligns with the need to address diagnostic challenges, mitigate disease severity, and strengthen public health strategies in light of the ongoing 2024 Bordetella pertussis resurgence.

Antibody in Breastmilk Following Pertussis Vaccination in Three-time Windows in Pregnancy

BACKGROUND

Pertussis-containing vaccines are routinely offered in the UK at 16-32 weeks of gestation and have been shown to be safe and effective, but there remains debate about the best timing for vaccination. Most research into this has focused on serologic immunity, but breastmilk is also important in infant immunity, and the amount of IgA in breastmilk may impact mucosal immunity. It is important to understand if the timing of vaccination in pregnancy affects the concentration of IgA in breastmilk.

METHODS

Participants recruited as part of the MAMA (Maternal Antibody in Milk After Vaccination) and OpTIMUM (Optimizing the Timing of Whooping Cough Immunisations in Mums) trials received a pertussis-containing vaccine during pregnancy, either before 24 weeks, between 24 and 27+6 weeks or between 28 and 31+6 weeks. Samples of colostrum within 24 hours of delivery and breastmilk at 14 days were collected. Pertussis toxin, pertactin, tetanus toxoid and diphtheria toxoid specific-IgA levels were measured using a multiplex immunoassay.

RESULTS

There was no difference in specific IgA levels against pertussis toxin, pertactin, tetanus toxoid and diphtheria toxoid between the groups vaccinated within different time periods. For all antigens, there was decay in antigen-specific IgA levels between colostrum and breastmilk at 14 days.

CONCLUSION

Our results suggest that the timing of administration of a pertussis-containing vaccine in pregnancy does not impact on antigen-specific IgA concentration in colostrum or breastmilk at 14 days.

Systematic Literature Review of Maternal Antibodies in Human Milk Following Vaccination During Pregnancy or Lactation: Tetanus, Pertussis, Influenza and COVID-19

BACKGROUND

Human milk (HM) contributes to infant disease protection through transfer of numerous bioactive molecules, including antibodies, though the mechanisms that determine HM antibody transfer and disease prevention in the infant are not fully understood. Even less is known about the transfer of, and infant protection afforded by, vaccine-induced HM antibodies following vaccination during pregnancy or lactation. This systematic literature review aimed to summarize published evidence on the presence, duration and function of HM antibodies against pertussis, influenza and coronavirus disease 2019 (COVID-19) induced by vaccination during pregnancy or lactation and the associated protection against infant illness and to identify gaps to guide future research in this area.

METHODS

Literature searches were conducted on September 15, 2023, in MEDLINE and Embase for articles published since January 2000.

RESULTS

Eighteen studies reporting vaccine-induced antibodies in HM or protection against infant illness were included. The collective evidence supports increased and sustained HM antibody levels following influenza and COVID-19 vaccination while antipertussis HM antibody levels remained elevated for only approximately 4 weeks postvaccination. COVID-19 booster vaccination during pregnancy was found to prolong the half-life of immunoglobulin G antibodies in HM relative to the COVID-19 primary vaccination series. Only 2 studies evaluated illness among breastfed infants born to mothers vaccinated during pregnancy; however, neither distinguished the independent effects of transplacental transfer of vaccine-induced antibodies, HM transfer of vaccine-induced antibodies and HM transfer of naturally acquired antibodies.

CONCLUSIONS

HM antibody levels are increased following pertussis, influenza and COVID-19 vaccination during pregnancy or lactation. However, the limited evidence base precludes conclusions about any incremental benefit of breastfeeding following vaccination during pregnancy versus the benefit of breastfeeding alone and studies designed to address this question are needed to inform vaccine policy.

COVID-19 booster enhances IgG mediated viral neutralization by human milk in vitro

Background

Facilitated by the inability to vaccinate, and an immature immune system, COVID-19 remains a leading cause of death among children. Vaccinated lactating mothers produce specific SARS-CoV-2 antibodies in their milk, capable of neutralizing the virus in vitro. Our objective for this study is to assess the effect of COVID-19 booster dose on SARS-CoV-2 antibody concentration and viral neutralization in milk, plasma, and infant stool.

Methods

Thirty-nine mothers and 25 infants were enrolled from December 2020 to May 2022. Milk, maternal plasma, and infants' stool were collected at various time-points up to 12 months following mRNA COVID-19 vaccination. A subgroup of 14 mothers received a booster dose. SARS-CoV-2 antibody levels and their neutralization capacities were assessed.

Results

Booster vaccination led to significantly higher IgG levels within human milk and breastfed infants' stool. In vitro neutralization of VSV-gfp-SARS-CoV-2-S-gp, a laboratory safe SARS-CoV-2 like pseudovirus, improved following the booster, with a 90% increase in plasma neutralization and a 60% increase in milk neutralization. We found that post-booster neutralization by human milk was highly correlated to SARS-CoV-2 IgG level. In support of our correlation result, Protein G column depletion of IgG in milk yielded a significant reduction in viral neutralization (p = 0.04).

Discussion

The substantial increase in neutralizing IgG levels in milk and breastfed infants' stool post-booster, coupled with the decrease in milk neutralization capabilities upon IgG depletion, underscores the efficacy of booster doses in augmenting the immune response against SARS-CoV-2 in human milk.

Exclusive Breastfeeding and Childhood Morbidity: A Narrative Review

Globally, diarrheal diseases and acute respiratory infections are the leading causes of morbidity and mortality in children under 5 years old. The benefits of exclusive breastfeeding in reducing the risk of gastrointestinal and respiratory infections are well documented. Optimal breastfeeding may potentially save the lives of about 800,000 children in low-income settings. Despite the evidence, around 63% of infants from birth to 6 months are not exclusively breastfed worldwide. We searched the literature published between 2010 and 2022 in Medline, Embase, and Scopus on the association between exclusive breastfeeding and infectious diseases. We selected and reviewed 70 relevant studies. Our findings expand and confirm the positive association between exclusive breastfeeding and reduced risk of a number of gastrointestinal, respiratory, and other infections in 60 out of 70 studies observed in both low- and high-income settings. Several studies analyzing exclusive breastfeeding duration reported that a longer exclusive breastfeeding duration is protective against many infectious diseases. This review also reported a lack of standardized definition for measuring exclusive breastfeeding in many studies. Overall, the results highlight the benefits of exclusive breastfeeding in many studies and suggests reporting exclusive breastfeeding in future studies using a consistent definition to enable better monitoring of exclusive breastfeeding rates.

Exclusive Breastfeeding and Vitamin D Supplementation: A Positive Synergistic Effect on Prevention of Childhood Infections?

Human milk is the best food for infants. Breastfeeding has been associated with a reduced risk of viral and bacterial infections. Breast milk contains the perfect amount of nutrients needed to promote infant growth, except for vitamin D. Vitamin D is crucial for calcium metabolism and bone health, and it also has extra-skeletal actions, involving innate and adaptive immunity. As exclusive breastfeeding is a risk factor for vitamin D deficiency, infants should be supplemented with vitamin D at least during the first year. The promotion of breastfeeding and vitamin D supplementation represents an important objective of public health.