Human Milk SARS-CoV-2 Antibodies up to 6 Months After Vaccination

The global status of human milk banking

Human milk provides essential nutrition for infants and holds many health benefits for infants and mothers. When a mother's own milk is not available for her infant, the World Health Organization recommends feeding donor human milk (DHM) from a human milk banking facility. DHM is human milk produced, collected then donated to a human milk bank (HMB). HMBs serve many vital functions, including screening donor mothers, then collecting, processing, storing, and allocating DHM to recipients. The first HMB opened in 1909, and today there are more than 700 HMBs globally. Unfortunately, HMB facilities are not present in all locales, with notable gaps in South Asia and Africa. Additionally, there are no global standards to guide HMB operational procedures. Even though most HMBs attempt to employ quality control systems to provide safe DHM, differences in community needs, resource availability, and a range of methods and policies to execute processes result in significant variations in DHM quality and HMB operations. Robust and collaborative systems that ensure safe and equitable access to DHM are needed. In this paper, we present a global snapshot of current human milk banking practices; review an interdisciplinary framework to guide and support HMB activities as an integrated part of health and newborn care systems; discuss factors that contribute to HMB sustainability; outline barriers to scaling HMBs worldwide; and highlight knowledge, policy, and research gaps. Developing global HMB guidance and rigorous, adaptable standards would strengthen efforts to improve newborn health.

Review of current best practices for human milk banking

Mother's/parent milk is the optimal way to feed infants and when unavailable, supplemental donor human milk is preferred. A safe supply of donor human milk should be available for all low birthweight infants for whom it has been shown to reduce morbidity. Human milk banking has been in existence for more than a century, although largely shut down during the 1980s, primarily due to fears of human immunodeficiency virus transmission. With renewed security in milk banking, has come an exponential growth in human donor milk use. Guidelines for milk banking have been published in many countries including Australia, France, India, Italy, Spain, Switzerland, the United Kingdom and the nonprofit organization PATH. The European Milk Bank Association and the Human Milk Banking Association of North America have also published recommendations for milk banks throughout Europe and North America, respectively. Although there is variability among these guidelines, there is general consensus on quality control measures required to provide a supply of safe donor milk. These measures include effective donor screening, safe collection, transport and storage of milk, standardized pasteurization and bacteriological testing. Operational considerations are also critical, such as appropriate training for staff, equipment maintenance and cleaning, protocol and record keeping and inspection and accreditation. Clearly delineating these key quality control measures provides an excellent foundation for establishing international guidelines. Acceptable modifications must be established for low- and middle-income countries that do not have sufficient resources; overly burdensome guidelines may make establishing a milk bank unnecessarily prohibitive. This review presents a summary of current best practices for human milk banking.

Challenges of breastfeeding during COVID-19 and baby friendly protocols adopted at a maternity health center in the northern Emirates of UAE: a comprehensive review

BACKGROUND

The outbreak of Coronavirus disease (COVID-19), caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS CoV-2) has caused worldwide panic in the global population taking people's lives, creating fear, and affecting mother-child relationships. Many questions were raised on the dangers of being infected with COVID-19 for newborns and safety concerns during feeding by COVID-19-positive mothers. Moreover, questions and doubts about the safety of the administration of vaccinations for nursing mothers are still open. This review attempts to fill the existing literature gap by exploring concepts concerning COVID-19 and breastfeeding mothers, the safety of vaccinations, the beneficial effects of breastfeeding on both mother and child, important hygiene recommendations for SARS-CoV-2 infected mothers, and possible solutions to optimize breastfeeding and safety precautions amidst the fear of emergence of novel variants.

METHODS

All relevant publications from Google Scholar, PubMed, Web of Science, and Scopus search engines from December 2019 to October 2022 related to SARS-CoV-2, breastfeeding, COVID-19, lactating guidelines, and vaccination were included using 'Breastfeeding AND vaccine AND SARS-CoV-2' as MESH TERMS. Apart from the literature review, existing maternity protocols followed in Northern UAE were gathered from lactation consultants practicing in the UAE.

RESULTS

Out of 19,391 records generated, only 24 studies were analyzed and summarized in this exhaustive review using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) flow chart. Previous studies suggest that breastmilk is predominantly the primary source of nutrition for neonates. Breast milk is a rich source of antibodies that help the baby to fight against infections including other benefits. Hygiene recommendations for suspected or confirmed COVID-19-infected mothers are required along with psychological and emotional support.

CONCLUSIONS

The administration of vaccinations should be advised and encouraged to protect the mothers with antibodies and the neonates by the passive transmission of antibodies through breast milk. This is a significant reason for not stopping breastfeeding even in case of COVID-19 infection. With adherence to proper hygiene methods, breastfeeding is recommended to be continued as the benefits greatly outweigh the risks.

Exploring the long-term seroprevalence of SARS-CoV-2 antibodies in infants born to women with clinical or laboratory-confirmed COVID-19

INTRODUCTION

Infants are at a higher risk of severe illness with COVID-19 infection compared to older children. While COVID-19 vaccination is not recommended for young infants, they can acquire maternally-derived anti-SARS-CoV-2 antibodies passively through the placenta and breastmilk. We described the persistence of infection-induced maternal antibodies in infant circulation at 9-12 months of age.

METHODOLOGY

This was a cross-sectional study nested within the INTERCOVID multinational cohort study. For each COVID positive pregnant woman, two unmatched consecutive COVID negative pregnant women were enrolled between April and September 2020. Women with a positive PCR test, radiographic signs consistent with COVID-19, or at least 2 predefined symptoms of COVID-19 were considered as COVID positive. For this nested cross-sectional study, all COVID positive and either one of the COVID negative participants recruited from the Aga Khan University, Pakistan were approached 9-12 months after delivery, and maternal and infant sera were collected for antibody detection.

RESULTS

Altogether, 83 mothers provided consent, of whom 32 (38.6 %) were COVID positive and 51 (61.4 %) were COVID negative during pregnancy. Anti-SARS-CoV-2 antibodies were present in 13 (41 %) infants born to COVID positive and 19 (39 %) infants born to COVID negative mothers (p = 0.87). The presence of reactive antibodies in infants at follow-up was associated with maternal antibodies at follow-up (OR:9.50, 95 % CI:2.03-44.42; p = 0.004). COVID infection occurred in 3 (6 %) infants born to COVID negative mothers while no infant born to a COVID positive mother had a history of infection (p = 0.27).

CONCLUSION

The presence of reactive anti-SARS-CoV-2 antibodies in infants at 9-12 months of age is associated with maternal seropositivity 9-12 months after delivery rather than maternal infection during pregnancy. Further studies are required to validate these findings and assess whether passive immunity in infants is protective against COVID-19 infection.

Persistence of COVID-19 Human Milk Antibodies After Maternal COVID-19 Vaccination: Systematic Review and Meta-Regression Analysis

The World Health Organization (WHO) declared COVID-19 a pandemic. The Centers for Disease Control and Prevention (CDC), WHO, and American College of Obstetricians and Gynecologists (ACOG) recommend vaccination of pregnant and lactating women, aiming to protect both mothers and their infants through transplacental and human milk antibody transmission. This study aims to assess the quantity of antibodies in human milk and determine the effect of time, vaccine type, and dose on antibody level. Single-arm prospective observational studies reporting the COVID-19-specific antibody level in human milk after COVID-19 vaccination during pregnancy or lactation were included. PubMed, Scopus, Cochrane, EBSCO, and Web of Science were searched from December 2019 to November 22, 2022. Data were extracted in a uniform Google sheet. A total of 2657 studies were identified. After the removal of duplicates and screening, 24 studies were included in the systematic review and meta-regression. Human milk COVID-19-specific antibody levels increased with subsequent vaccine doses, as reflected by a positive relationship for the second (coefficient=0.91, P-value 0.043 for IgA and coefficient=1.77, P-value 0.009 for IgG) and third (coefficient=1.23, P-value 0.0029 for IgA and coefficient=3.73, P-value 0.0068 for IgG) doses. The antibody level exhibited a weak positive relationship with the follow-up time (coefficient=0.13, P-value 0.0029 for IgA and coefficient=0.18, P-value 0.016 for IgG). Only one of the 38 infants showed detectable COVID-19 IgM and IgA antibody levels in their blood. There was an increase in the neutralizing activity of COVID-19 antibodies in human milk following the COVID-19 vaccination. From the analysis of published data, we found high positive levels of antibodies in human milk that increased with subsequent doses. Additionally, the human milk antibodies exhibit a positive neutralizing effect. Only one infant had detectable COVID-19 IgM+IgA antibodies in the blood. Further research is needed to discuss infant protection through a mother's vaccination.

SARS-CoV-2 antibodies and their neutralizing capacity against live virus in human milk after COVID-19 infection and vaccination: prospective cohort studies

BACKGROUND

There is limited understanding of the impact of coronavirus disease 2019 (COVID-19) infection and vaccination type and interval on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) human milk antibodies and their neutralizing capacity.

OBJECTIVES

These cohort studies aimed to determine the presence of antibodies and live virus neutralizing capacity in milk from females infected with COVID-19, unexposed milk bank donors, and vaccinated females and examine impacts of vaccine interval and type.

METHODS

Milk was collected from participants infected with COVID-19 during pregnancy or lactation (Cohort-1) and milk bank donors (Cohort-2) from March 2020-July 2021 at 3 sequential 4-wk intervals and COVID-19 vaccinated participants with varying dose intervals (Cohort-3) (January-October 2021). Cohort-1 and Cohort-3 were recruited from Sinai Health (patients) and through social media. Cohort-2 included Ontario Milk Bank donors. Milk was examined for SARS-CoV-2 antibodies and live virus neutralization.

RESULTS

Of females with COVID-19, 53% (Cohort-1, n = 55) had anti-SARS-CoV-2 IgA antibodies in ≥1 milk sample. IgA+ samples (40%) were more likely neutralizing than IgA- samples (odds ratio [OR]: 2.18; 95% confidence interval [CI]: 1.03, 4.60; P = 0.04); however, 25% of IgA- samples were neutralizing. Both IgA positivity and neutralization decreased ∼6 mo after symptom onset (0-100 compared with 201+ d: IgA OR: 14.30; 95% CI: 1.08, 189.89; P = 0.04; neutralizing OR: 4.30; 95% CI: 1.55, 11.89; P = 0.005). Among milk bank donors (Cohort-2, n = 373), 4.3% had IgA antibodies; 23% of IgA+ samples were neutralizing. Vaccination (Cohort-3, n = 60) with mRNA-1273 and shorter vaccine intervals (3 to <6 wk) resulted in higher IgA and IgG than BNT162b2 (P < 0.04) and longer intervals (6 to <16 wk) (P≤0.02), respectively. Neutralizing capacity increased postvaccination (P = 0.04) but was not associated with antibody positivity.

CONCLUSIONS

SARS-CoV-2 infection and vaccination (type and interval) impacted milk antibodies; however, antibody presence did not consistently predict live virus neutralization. Although human milk is unequivocally the best way to nourish infants, guidance on protection to infants following maternal infection/vaccination may require more nuanced messaging. This study was registered at clinicaltrials.gov as NCT04453969 and NCT04453982.

A narrative review of COVID-19 vaccination in pregnancy and breastfeeding

The Coronavirus pandemic has affected millions of people due to the spread of the Severe acute respiratory syndrome Coronavirus-2 (SARS-CoV-2) virus. Pregnant individuals and infants are most vulnerable given the increased risk of developing severe complications from SARS-CoV-2 infection. Recently, COVID-19 vaccination is recommended for pregnant women and infants starting at 6 months of age to prevent disease contraction and minimize disease severity. We conducted a review of the literature on COVID-19 vaccination to discuss vaccine safety and efficacy, immunity after maternal vaccination, transplacental transfer and persistence of antibodies, and public health implications. Current evidence supports the safety and efficacy of vaccination during pregnancy. Maternal vaccination provides greater antibody persistence in infants compared to immunity from natural infection. Furthermore, vaccination has demonstrated an increased rate of passive antibody transfer through the placenta and breast milk. Public health interventions are important in achieving herd immunity and ultimately ending the pandemic. IMPACT: This article highlights the benefits of COVID-19 vaccination during pregnancy with a review of the data describing safety and efficacy, passive and active immunity after maternal immunization, trans-placental transfer and persistence of protective antibodies, and public health implications. With this information, healthcare providers can provide up-to-date knowledge to their pregnant patients to help them form an informed decision on vaccination and combat vaccine hesitancy.

The protective role of maternal genetic immunization on maternal-fetal health and welfare

Pregnancy is a critical period associated with alterations in physiologic, biologic, and immunologic processes, which can affect maternal-fetal health through development of several infectious diseases. At birth, neonates have an immature immune system that makes them more susceptible to severe viral infections and diseases. For this reason, different maternal nutritional and immunization interventions have been used to improve the immune and health status of the mother and her neonate through passive immunity. Here, we reviewed the protective role of maternal immunization with different types of vaccines, especially genetic vaccines, during pregnancy in maternal-fetal health, immune response, colostrum quality, immune response, and anti-oxidative status. For this purpose, we have used different scientific databases (PubMed and Google Scholar) and other official web pages. We customized the search period range from the year 2000 to 2023 using the key words "maternal immunization" OR "gestation period/pregnancy" OR "genetic vaccination" OR "maternal-fetal health" OR "micronutrients" OR "neonatal immunity" "oxidative stress" OR "colostrum quality". The evidence demonstrated that inactivated or killed vaccines produced significant immune protection in the mother and fetus. Furthermore, most recent studies have suggested that the use of genetic vaccines (mRNA and DNA) during pregnancy is efficient at triggering the immune response in mother and neonate without the risk of undesired pregnancy outcomes. However, factors such as maternal redox balance, nutritional status, and the timing of immunization play essential roles in regulating immune response inflammatory status, antioxidant capacity, and the welfare of both the pregnant mother and her newborn.

Viruses and Human Milk: Transmission or Protection?

Human milk (HM) is considered the best source of nutrition for infant growth and health. This nourishment is unique and changes constantly during lactation to adapt to the physiological needs of the developing infant. It is also recognized as a potential route of transmission of some viral pathogens although the presence of a virus in HM rarely leads to a disease in an infant. This intriguing paradox can be explained by considering the intrinsic antiviral properties of HM. In this comprehensive and schematically presented review, we have described what viruses have been detected in HM so far and what their potential transmission risk through breastfeeding is. We have provided a description of all the antiviral compounds of HM, along with an analysis of their demonstrated and hypothesized mechanisms of action. Finally, we have also analyzed the impact of HM pasteurization and storage methods on the detection and transmission of viruses, and on the antiviral compounds of HM. We have highlighted that there is currently a deep knowledge on the potential transmission of viral pathogens through breastfeeding and on the antiviral properties of HM. The current evidence suggests that, in most cases, it is unnecessarily to deprive an infant of this high-quality nourishment and that the continuation of breastfeeding is in the best interest of the infant and the mother.

SARS-CoV-2 Antibody Profiles in Maternal Serum and Breast Milk Following mRNA COVID-19 Vaccination: A Longitudinal Prospective Observational Cohort Study

COVID-19 vaccination during pregnancy protects infants against symptomatic COVID-19. Vaccination of lactating mothers may offer additional protection, but our understanding of immune responses in breast milk is limited. We, therefore, performed a single-center prospective cohort study of lactating mothers who received a COVID-19 mRNA primary vaccine series to evaluate the durability, breadth, and neutralizing capacity of the antibody responses in breast milk. Spike IgG- and IgA-binding antibodies of ancestral SARS-CoV-2 in serum and breast milk were quantified over 9 months using Meso Scale Discovery (MSD) V-PLEX assays, and ancestral titers were compared to four variants of concern (Alpha, Beta, Delta, Gamma) at a single time point. Neutralizing antibodies against ancestral SARS-CoV-2 and Omicron BA.4/5 were compared before and after vaccination using a pseudovirus-neutralization assay. Eleven lactating mothers received either Pfizer BNT162b2 (7/11) or Moderna mRNA-1273 (4/11) vaccine primary series. IgG and IgA titers increased in serum and breast milk following each dose, peaking 1-4 weeks after series completion. Titers remained significantly elevated for 7-9 months, except for in breast milk IgA which returned to baseline within 1 month. Furthermore, binding antibodies against all included variants were detected in breast milk collected 1-3 weeks after series completion. However, while vaccination induced a strong neutralizing response against ancestral SARS-CoV-2 in serum and more modest response in breast milk, it did not induce neutralizing antibodies against Omicron BA.4/5 in either specimen type. This study demonstrates that maternal COVID-19 mRNA vaccination may enhance immune protection for infants through breast milk via increased IgG- and IgA-binding-and-neutralizing antibodies; although, variant-specific boosters may be required to optimize immune protection.

Perinatal care and breastfeeding education during the COVID-19 pandemic: Perspectives from Kenyan mothers and healthcare workers

The impact of the COVID-19 pandemic on breastfeeding (BF) practices in low- and middle-income countries (LMICs) is not well understood. Modifications in BF guidelines and delivery platforms for breastfeeding education during the COVID-19 pandemic are hypothesised to have affected BF practices. We aimed to understand the experiences with perinatal care, BF education and practice among Kenyan mothers who delivered infants during the COVID-19 pandemic. We conducted in-depth key informant interviews with 45 mothers who delivered infants between March 2020 and December 2021, and 26 health care workers (HCW) from four health facilities in Naivasha, Kenya. While mothers noted that HCWs provided quality care and BF counselling, individual BF counselling was cited to be less frequent than before the pandemic due to altered conditions in health facilities and COVID-19 safety protocols. Mothers stated that some HCW messages emphasised the immunologic importance of BF. However, knowledge among mothers about the safety of BF in the context of COVID-19 was limited, with few participants reporting specific counselling or educational materials on topics such as COVID-19 transmission through human milk and the safety of nursing during a COVID-19 infection. Mothers described COVID-19-related income loss and lack of support from family and friends as the major challenge to practising exclusive breastfeeding (EBF) as they wished or planned. COVID-19 restrictions limited or prevented mothers' access to familial support at facilities and at home, causing them stress and fatigue. In some cases, mothers reported job loss, time spent seeking new means of employment and food insecurity as causes for milk insufficiency, which contributed to mixed feeding before 6 months. The COVID-19 pandemic created changes to the perinatal experience for mothers. While messages about the importance of practising EBF were provided, altered HCW education delivery methods, reduced social support and food insecurity limit EBF practices for mothers in this context.

Breastmilk from COVID-19 negative lactating mothers shows neutralizing activity against SARS-COV-2

Breastmilk protects newborns from infections through specific and nonspecific compounds. This study investigated the neutralizing activity against SARS-CoV-2 of breastmilk from SARS-CoV-2 negative, unvaccinated mothers, and compared it to that from infected nursing mothers. We enrolled women after COVID-19 swab testing results upon maternity admission, and divided them into two groups: group A, COVID-19-positive mothers, and group B, negative mothers. Breastmilk was randomly sampled at 2, 7, and 20 days postpartum. We collected 19 samples for Group A and 41 for Group B. A microneutralization assay was used to determine the 50% neutralization (NT50) titre. The presence of neutralizing antibodies was also determined. Group A had 100% neutralizing samples at 2 days postpartum (T0), declining 7 days postpartum (T1) and 20 days postpartum (T2). Group B samples exhibited neutralizing activity mostly at 7 days postpartum (T1) (90%). Negative mothers' samples showed no correlation between NT50 titres and antibodies' presence, suggesting that non-specific breastmilk components may exert antiviral action against SARS-CoV-2.

Vertical transmission and maternal passive immunity post-SARS-CoV-2

Since 2020, the highly contagious nature and various transmission routes of SARS-CoV-2 have rendered the pandemic interminable. Vertical transmission (VT) through the placenta and breast milk, which is frequent for certain virus types, is thought to exist for SARS-CoV-2 and is hypothesized by many researchers. Conversely, antibodies are produced to counteract the effect of viruses. Since newborns' immunologic system cannot produce proper antibodies, maternal antibodies are usually transferred from mother to infant/fetus to meet the need. This theory leads to the hypothesis of transmission of antibodies through the placenta and breast milk following SARS-CoV-2 infection or vaccination. This paper further discusses these hypotheses, considering consequences of fetus/infant harm versus benefit.

Sustained and Boosted Antibody Responses in Breast Milk After Maternal SARS-CoV-2 Vaccination

Background: Pregnant and lactating women were not included in the initial large vaccine clinical trials for SARS-CoV-2 (COVID) infection. Delineating the antibody titers in serum and breast milk of lactating women is important to determine the safety and benefits of vaccination in this special population. Objective: To investigate COVID vaccinations in breastfeeding dyads and effects on lactation, the Antibody Detection of Vaccine-Induced Secretory Effects trial (ADVISE) prospectively evaluated anti-COVID antibodies in serum and breast milk after initial paired and booster vaccines. Methods: This is a prospective longitudinal surveillance cohort study of lactating women. Eligibility criteria included ≥18 years of age, currently lactating, and at enrollment either received COVID vaccination within the past 60 days or planning vaccination within 60 days. Results: Among 63 lactating mothers, COVID vaccination led to breast milk secretory IgA (sIgA) and IgG antibodies with consistent viral neutralizing activity. Milk sIgA titers increased further after second vaccination and were prolonged after a third booster dose, including women with extended breastfeeding beyond 12 months. Milk IgG antibody titers were higher and more sustained than sIgA. Antibody titers were not associated with individual dyad characteristics or vaccine manufacturer. Vaccine-induced antibodies from milk were not detected in infant circulation. Conclusions and Relevance: Maternal COVID vaccination during lactation is well tolerated and generates sustained and boosted antibody responses in breast milk. COVID-specific sIgA and IgG antibodies with neutralizing activity are found in breast milk, including boosted mothers who continue breastfeeding beyond 12 months. These data support universal COVID vaccinations for all lactating mothers, including booster immunizations during extended breastfeeding (NCT04895475).

Assessment of human milk samples obtained pre and post-influenza vaccination reveals a poor boosting of seasonally-relevant, hemagglutinin-specific antibodies

Introduction

Influenza (flu) vaccination prevented over 100,000 hospitalizations and 7000 deaths from flu over the 2019-2020 season in the USA. Infants <6 months are the most likely to die from flu, though flu vaccines are only licensed for infants >6 months old. Therefore, it is recommended that flu vaccination occur during pregnancy, as this reduces severe complications; however, vaccination rates are suboptimal, and vaccination is also recommended postpartum. For breast/chest-fed infants, the vaccine is believed to elicit protective and robust seasonally-specific milk antibody (Ab). Few comprehensive studies exist examining Ab responses in milk after vaccination, with none measuring secretory Ab (sAb). Determining whether sAbs are elicited is critical, as this Ab class is highly stable in milk and mucosae.

Methods

In the present study, our aim was to determine to what extent specific Ab titers in the milk of lactating people were boosted after seasonal influenza vaccination. Over the 2019-2020 and 2020-2021 seasons, milk was obtained pre- and post-vaccination and assessed for specific IgA, IgG, and sAb against relevant hemagglutinin (HA) antigens by a Luminex immunoassay.

Results

IgA and sAb were not found to be significantly boosted, while only IgG titers against B/Phuket/3073/2013, included in vaccines since 2015, exhibited an increase. Across the 7 immunogens examined, as many as 54% of samples exhibited no sAb boost. No significant differences for IgA, sAb, or IgG boosting were measured between seasonally-matched versus mismatched milk groups, indicating boosting was not seasonally-specific. No correlations between IgA and sAb increases were found for 6/8 HA antigens. No boost in IgG- or IgA-mediated neutralization post vaccination was observed.

Discussion

This study highlights the critical need to redesign influenza vaccines with the lactating population in mind, wherein the aim should be to elicit a potent seasonally-specific sAb response in milk. As such, this population must be included in clinical studies.

Anti-SARS-CoV-2 Immunoglobulins in Human Milk after Coronavirus Disease or Vaccination-Time Frame and Duration of Detection in Human Milk and Factors That Affect Their Titers: A Systematic Review

Human milk (HM) of mothers infected with or vaccinated against SARS-CoV-2 contains specific immunoglobulins, which may protect their offspring against infection or severe disease. The time frame and duration after infection or vaccination, during which these immunoglobulins are detected in HM, as well as the major factors that influence their levels, have not been fully elucidated. This systematic review aimed to collect the existing literature and describe the immune response, specifically regarding the immunoglobulins in HM after COVID-19 disease or vaccination in non-immune women. We conducted a systematic search of PubMed and Scopus databases to identify studies published up until 19 March 2023. In total, 975 articles were screened, and out of which 75 were identified as being relevant and were finally included in this review. Infection by SARS-CoV-2 virus primarily induces an IgA immune response in HM, while vaccination predominantly elevates IgG levels. These immunoglobulins give HM a neutralizing capacity against SARS-CoV-2, highlighting the importance of breastfeeding during the pandemic. The mode of immune acquisition (infection or vaccination) and immunoglobulin levels in maternal serum are factors that seem to influence immunoglobulin levels in HM. Further studies are required to determine the impact of other factors, such as infection severity, lactation period, parity, maternal age and BMI on immunoglobulin level in HM.

Safety and Efficacy of Coronavirus Disease 2019 (COVID-19) mRNA Vaccines During Lactation

In this review, we summarize the data on the safety and side-effect profile of coronavirus disease 2019 (COVID-19) vaccines during lactation to date, review what is known about mRNA vaccine components in breast milk, and discuss the efficacy of COVID-19 vaccines in providing immune protection for the breastfeeding infant. The Centers for Disease Control and Prevention and the American College of Obstetricians and Gynecologists recommend that lactating individuals receive COVID-19 mRNA vaccines and stay up to date on booster doses, including the bivalent COVID-19 booster. The lack of serious side effects in mothers or infants across numerous large studies and registries of COVID-19 vaccination in pregnancy and lactation is reassuring. Although small quantities of mRNA may be transiently detectable in breast milk after maternal vaccination, there are no data demonstrating that vaccine mRNA can survive the infant gastrointestinal tract and no evidence that breast milk from lactating individuals who have received a COVID-19 mRNA vaccine can cause harm to breastfeeding infants. In contrast, numerous studies demonstrate that the breast milk of vaccinated individuals contains severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific functional antibodies and T cells, which benefit the breastfeeding infant's developing immune system. Transfer of SARS-CoV-2-specific antibodies from mother to infant is highest when vaccination occurs during pregnancy compared with lactation, because the breastfeeding infant receives both long-lasting antibodies through the placenta and breast-milk antibodies through breast milk. With clear data demonstrating efficacy and safety and no data demonstrating harm to mother or infant after COVID-19 vaccine administration during lactation, any recommendations to avoid vaccination while breastfeeding or to withhold breast milk from the infant for any period of time after vaccination are not supported by available evidence.

Immunisation against COVID-19 in Pregnancy and of Women Planning Pregnancy

Following reports of the first human SARS-CoV2 infection in December 2019 from Wuhan Province, China, there was such rapid spread that by March 2021, the World Health Organization (WHO) had declared a pandemic. Over 6.5 million people have died from this infection worldwide, although this is most likely an underestimate. Until vaccines became available, mortality and severe morbidity were costly in terms of life lost as well as the cost of supporting the severely and acutely ill. Vaccination changed the landscape, and following worldwide adoption, life has gradually been returning to normal. The speed of production of the vaccines was unprecedented and undoubtedly ushered in a new era in the science of fighting infections. The developed vaccines were on the already known platforms for vaccine delivery: inactivated virus, virus vector, virus-like particles (VLP) subunit, DNA and mRNA. The mRNA platform was used for the first time to deliver vaccines to humans. An understanding of these platforms and the pros and cons of each are important for clinicians who are often challenged by the recipients on the advantages and risks of these vaccines. These vaccines have so far and reassuringly been shown to be safe in reproduction (with no effect on gametes) and pregnancy (not associated with congenital malformations). However, safety remains paramount and continuing vigilance is critical, especially against rare fatal complications such as vaccine-induced thrombocytopenia and myocarditis. Finally, the waning immunity months after vaccination means repeated immunisation is likely to be ongoing, but just how often and how many such revaccinations should be recommended remains uncertain. Research into other vaccines and alternate delivery methods should continue as this infection is likely to be around for a long time.

Detection of SARS-CoV-2-Specific Antibodies in Human Breast Milk and Their Neutralizing Capacity after COVID-19 Vaccination: A Systematic Review

SARS-CoV-2 is the virus that causes the infectious disease known as Corona Virus Disease 2019 (COVID-19). The severe impact of the virus on humans is undeniable, which is why effective vaccines were highly anticipated. As of 12 January 2022, nine vaccines have obtained Emergency Use Listing by the World Health Organization (WHO), and four of these are approved or authorized by the Centers for Disease Control and Prevention (CDC) in the United States. The initial clinical trials studying COVID-19 vaccine efficacy excluded pregnant and lactating individuals, meaning that data on the effects of the vaccine on breast milk were lacking. Until today, none of the authorized vaccines have been approved for use in individuals under six months. During the first months of life, babies do not produce their own antibodies; therefore, antibodies contained in their mothers' breastmilk are a critical protective mechanism. Several studies have shown the presence of SARS-CoV-2 antibodies in the breast milk of women who have been vaccinated or had been naturally infected. However, whether these are protective is still unclear. Additionally, research on the BNT162b2 mRNA vaccine developed by Pfizer-BioNTech and the mRNA-1273 vaccine developed by Moderna suggests that these vaccines do not release significant amounts, if any, of mRNA into breast milk. Hence, there is no evidence that vaccination of the mother poses any risk to the breastfed infant, while the antibodies present in breast milk may offer protection against the virus. The primary objective of this systematic review is to summarize the current understanding of the presence of immunoglobulins in human milk that are elicited by SARS-CoV-2 vaccines and to evaluate their ability to neutralize the virus. Additionally, we aim to quantify the side effects experienced by lactating mothers who have been vaccinated, as well as the potential for adverse effects in their infants. This study is critical because it can help inform decision-making by examining the current understanding of antibody secretion in breastmilk. This is particularly important because, although the virus tends to be less severe in younger individuals, infants who contract the disease are at a higher risk of requiring hospitalization compared to older children.

COVID-19 Vaccines during Pregnancy and Breastfeeding: A Systematic Review

Background: Pregnant and breastfeeding women received unclear recommendations regarding COVID-19 vaccination at the beginning of the pandemic, as they were not included in the initial clinical trials. This systematic review aims to provide an update regarding COVID-19 vaccines during pregnancy and breastfeeding. Methods: The systematic review was carried out through a literature search in Medline/Pubmed. Studies were selected if they included information regarding COVID-19 vaccination during pregnancy and breastfeeding. The PRISMA guidelines for systematic reviews were followed. Results: A total of 33 studies were included. The main adverse effect is pain at the injection site, as in the general population. Adverse effects are more frequent after the second dose, being slightly more frequent after the Moderna vaccine. COVID-19 vaccination reduces the risk of severe COVID-19 in pregnant women. Additionally, COVID-19 vaccination induces artificial active immunogenicity in the mother and natural passive immunogenicity in the child. Breastmilk straddles both immediate antibody-mediated and long-lived cellular-mediated immune protection. Regarding neonatal benefits, vaccination is associated with a larger and more stable Immunoglobulin G response, while COVID-19 Infection is associated with a rapid and long-lasting Immunoglobulin A response. Conclusions: COVID-19 vaccines are not only suggested but strongly recommended for pregnant and breastfeeding populations to protect mothers and newborns.

SARS-CoV-2 spike RBD-specific IgA and IgG antibodies in breast milk after vaccination with the protein subunit vaccine Abdala

Background

COVID-19 vaccines that trigger a strong secretory antibody response in breast milk may achieve effective passive protection of vulnerable newborns and breastfed infants of immunized mothers. The aim of this work was to investigate the presence of SARS-CoV-2 spike RBD-specific IgA and IgG antibodies in breast milk, 5 and 9 weeks after vaccination with 3 doses of the protein subunit vaccine Abdala, compared to those found in breast milk from COVID-19-recovered women, collected at least 40 days after the infection.

Methods

SARS-CoV-2 spike RBD-specific IgA and IgG antibodies were semi-quantified by indirect ELISA, using a homemade standard generated by pooling twenty breast milk samples with high absorbance values according to preliminary data. The validity of the standard curves was proved following the European Medicines Agency Guideline. Two breast milk samples from 2 unvaccinated women who had not been infected with COVID-19 were included as negative controls. Potentially neutralizing antibodies was assessed by a SARS-CoV-2 surrogate virus neutralization test.

Results

High levels of anti-RBD IgA antibodies were detected in breast milk samples 9 weeks after vaccination and anti-RBD IgG antibodies rise from the fifth to the ninth week. In the post-COVID-19 time that was evaluated, the IgG-type response was notably higher compared to both post-vaccination periods. Neutralizing antibody titers were similar in breast milk from vaccinated and COVID-19 recovered women.

Conclusions

This is the first report about the immune response in breast milk after the administration of a COVID-19 protein subunit vaccine, which could provide analogous protection to that conferred by SARS-CoV-2 infection. This implies a potential passive immunity that breastfed infants receive from their mothers vaccinated with Abdala.

Pandemic policies and breastfeeding: A cross-sectional study during the onset of COVID-19 in the United States

The United States is one of the few countries, and the only high-income country, that does not federally mandate protection of postpartum employment through paid postpartum maternity and family leave policies. At the onset of the COVID-19 pandemic in the U.S., stay-at-home orders were implemented nationally, creating a natural experiment in which to document the effects of de facto paid leave on infant feeding practices in the first postpartum year. The purpose of this cross-sectional, mixed-methods study was to describe infant and young child feeding intentions, practices, decision-making, and experiences during the first wave of the COVID-19 pandemic in the U.S. Quantitative and qualitative data were collected March 27-May 31, 2020 via online survey among a convenience sample of respondents, ages 18 years and older, who were currently feeding a child 2 years of age or younger, yielding 1,437 eligible responses. Nearly all (97%) respondents indicated an intention to feed their infant exclusively with human milk in the first 6 months. A majority of respondents who were breastfeeding (66%) reported no change in breastfeeding frequency after the implementation of COVID-19 stay-at-home orders. However, thirty-one percent indicated that they breastfed more frequently due to stay-at-home orders and delayed plans to wean their infant or young child. Key themes drawn from the qualitative data were: emerging knowledge and perceptions of the relationship between COVID-19 and breastfeeding, perceptions of immune factors in human milk, and the social construction of COVID-19 and infant and young child feeding perceptions and knowledge. There were immediate positive effects of stay-at-home policies on human milk feeding practices, even during a time of considerable uncertainty about the safety of breastfeeding and the transmissibility of SARS-CoV-2 via human milk, constrained access to health care services and COVID-19 testing, and no effective COVID-19 vaccines. Federally mandated paid postpartum and family leave are essential to achieving more equitable lactation outcomes.

Overview of Breastfeeding Under COVID-19 Pandemic

During the global pandemic of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), pregnant and lactating women are at higher risk of infection. The potential of viral intrauterine transmission and vertical transmission by breastfeeding has raised wide concerns. Breastmilk is rich in nutrients that contribute to infant growth and development, and reduce the incidence rate of infant illness and death, as well as inhibit pathogens significantly, and protect infants from infection. Although it is controversial whether mothers infected with COVID-19 should continue to breastfeed, many countries and international organizations have provided recommendations and guidance for breastfeeding. This review presents the risks and benefits of breastfeeding for mothers infected with COVID-19, and the reasons for the absence of SARS-CoV-2 active virus in human milk. In addition, the antiviral mechanisms of nutrients in breastmilk, the levels of SARS-CoV-2 specific antibodies in breastmilk from COVID-19 infected mothers and vaccinated mothers are also summarized and discussed, aiming to provide some support and recommendations for both lactating mothers and infants to better deal with the COVID-19 pandemic.

Vaccine Protection Through Placenta and Breastfeeding: The Unmet Topic in COVID-19 Pandemic

The coronavirus disease 2019 (COVID-19) pandemic has turned pregnant women’s healthcare into a worldwide public health challenge. Although initial data did not demonstrate pregnancy as a more susceptible period to severe outcomes of acute severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) infection, there are an increasing number of reports showing that not only pregnant women might be at significantly higher risk than non-pregnant women by COVID-19 but also the fetus. These findings may be related to adaptive changes that occur during pregnancy, such as the reduction in the residual respiratory capacity, the decrease in viral immune responses, and the increased risk for thromboembolic events. Additionally, despite the SARS-CoV-2 vertical transmission evidence being uncommon, maternal illness severity might reflect serious perinatal and neonatal outcomes. Thus, protecting the maternal–fetal dyad against COVID-19 is critical. Even though pregnant women initially were excluded from vaccine trials, several studies have provided safety and efficacy of the overall vaccine COVID-19 platforms. Vaccination during pregnancy becomes a priority and can generate benefits for both the mother and newborn: maternal neutralizing antibodies are transmitted through the placenta and breastfeeding. Moreover, regarding passive immunization, human milk contains other bioactive molecules and cells able to modulate the newborn’s immune response, which can be amplified after the vaccine. Nonetheless, many issues remain to be elucidated, considering the magnitude of the protective immunity transferred, the duration of the induced immunity, and the optimal interval for pregnant immunization. In this review, we assessed these unmet topics supported by literature evidence regarding the vaccine’s immunogenicity, pregnancy immune heterogeneity, and the unique human milk antiviral features.

Coronavirus Disease 2019 Vaccine Booster Effects Are Seen in Human Milk Antibody Response

Infants remain at high risk for severe coronavirus disease 2019 (COVID-19). Human milk contains high levels of protective SARS CoV-2 specific antibodies post-infection and primary vaccine series, but levels decline over time. We hypothesized that the COVID-19 booster vaccine augment antibody production and the protection afforded to human milk-fed infants. We prospectively enrolled pregnant or lactating mothers planning to receive COVID-19 vaccination. We measured human milk IgG, IgA, and IgM antibodies targeting the SARS CoV-2 receptor binding domain within the spike protein and human milk neutralization activity against SARS CoV-2 in 10 lactating mothers from pre-COVID-19 primary series vaccine to post-booster dose. Human milk SARS CoV-2 specific IgG increased significantly from pre- to post-booster levels (median OD 0.33 vs. 2.02, P = 0.002). The IgG levels post-booster were even higher than the peak level after the primary series (2.02 vs. 0.95, P = 0.03). The increase in SARS CoV-2 specific IgA levels was not significant (0.10 vs. 0.33, P = 0.23). There was a strong correlation between paired maternal blood and milk IgG and IgA levels (IgG rho 0.52, P < 0.001, IgA rho 0.31, P = 0.05). Post-booster neutralizing activity was elevated compared to pre-booster levels (66% vs. 12% inhibition, P = 0.002). COVID-19 vaccine booster elicits SARS CoV-2 specific antibodies in human milk at higher levels compared to the initial primary series. This finding suggests that three doses of COVID-19 mRNA vaccination leads to improved mucosal response in human milk and reinforces current guidance recommending all pregnant or lactating mothers receive full COVID-19 vaccine courses with a booster dose.

Quantification and progress over time of specific antibodies against SARS-CoV-2 in breast milk of lactating women vaccinated with BNT162b2 Pfizer-BioNTech COVID-19 vaccine (LacCOVID)

Background

Several observational studies demonstrated the passage of postvaccine antibodies through breast milk in women vaccinated against coronavirus disease 2019 (COVID-19), mostly with messenger RNA (mRNA)–based vaccines, but lacked long-term data.

Methods

A 6-month prospective cohort study was performed to determine severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine–induced antibody levels in the breast milk of 33 lactating healthcare workers at different timepoints after mRNA BNT162b2 Pfizer-BioNTech COVID-19 vaccination. Moreover, we examined the correlation of SARS-CoV-2 antibody levels between serum and breast milk, adverse events related to vaccination, and rate of SARS-CoV-2 infections.

Results

Mothers’ median age was 38 (interquartile range [IQR], 36–39) years and 15 (IQR, 10–22) months for infants. Median (IQR) SARS-CoV-2 immunoglobulin G (IgG) spike protein subunit S1 (S1) vaccine–induced levels at different timepoints for serum–milk pairs were 519 (234–937) to 1 (0–2.9) arbitrary units (AU)/mL at 2 weeks after first dose and 18 644 (9923–29 264) to 78 (33.7–128), 12 478 (6870–20 801) to 50.4 (24.3–104), 4094 (2413–8480) to 19.9 (10.8–51.9), 1350 (831–2298) to 8.9 (7.8–31.5) AU/mL at 2, 4, 12 and 24 weeks after second dose, respectively. We observed a positive correlation of antibody levels between serum and breast milk, no serious adverse events related to vaccination, and 2 (6%) COVID-19 vaccine breakthrough infections.

Conclusions

Women vaccinated with Pfizer-BioNTech transmit antibodies into breast milk with a positive correlation with serum levels. Both decreased over time in a 6-month follow-up.

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.

Maternal vaccination as an additional approach to improve the protection of the nursling: Anti-infective properties of breast milk

Human milk constitutes a secretion with unique functions of both nourishing the nursling and providing protection against enteric and respiratory infections, mainly due to its content of secretory IgA antibodies but also due to the presence of a plethora of bioactive factors. Specific IgA antibodies are produced locally by plasma cells derived from B lymphocytes that migrate from other mucosae to the mammary gland during lactation, particularly from the gastrointestinal and respiratory tracts. Therefore, here, the authors will provide a comprehensive review of the content and functions of different nutritional and bioactive anti-infectious components from breast milk, such as oligosaccharides, lactoferrin, haptocorrin, α-lactalbumin, k-casein, lysozyme, lactoperoxidase, mucin, fatty acids, defensins, cytokines and chemokines, hormones and growth factors, complement proteins, leukocytes and nucleic acids, including microRNAs, among many others, and the induction of antibody responses in breast milk after maternal vaccination with several licensed vaccines, including the anti-SARS-CoV-2 vaccine preparations used worldwide. Currently, in the midst of the pandemic, maternal vaccination has re-emerged as a crucial source of passive immunity to the neonate through the placenta and breastfeeding, considering that maternal vaccination can induce specific antibodies if performed during pregnancy and after delivery. There have been some reports in the literature about milk IgA antibodies induced by bacterial antigens or inactivated virus vaccines, such as anti-diphtheria-tetanus-pertussis, anti-influenza viruses, anti-pneumococcal and meningococcal polysaccharide preparations. Regarding anti-SARS-CoV-2 vaccines, most studies demonstrate elevated levels of specific IgA and IgG antibodies in milk with virus-neutralizing ability after maternal vaccination, which represents an additional approach to improve the protection of the nursling during the entire breastfeeding period.