SARS-CoV-2 antibodies persist in breast milk after 2 or 3 doses of COVID-19 vaccine

The World Health Organization (WHO) recommends that infants be breastfed for at least 6 months, continue breastfeeding for at least 2 years, and introduce complementary foods gradually.

study: Milk Antibody Response and Impact on Infant Protection After Third Dose of COVID-19 mRNA Vaccine and SARS-CoV-2 Breakthrough InfectionImage Credit: Tomsickova Tatyana / Shutterstock.com

Breast milk overview

Breastfeeding is associated with short- and long-term protective effects against several diseases. For example, duration and exclusivity of breastfeeding are associated with reduced risk of respiratory infections in infants.

Human breast milk is composed of several factors, including enzymes, cytokines, antibodies, extracellular vesicles and immune cells that provide antiviral protection to infants. In addition, the breast itself also provides passive immunity to infants in the form of immunoglobulin G (IgG), IgM, and IgA, despite having no direct mucosal surface.

The secretory form of IgA (sIgA) is the predominant antibody found in human breast milk, but the levels of IgG present in the monomeric form are low compared to both IgA and IgM.

Breastfeeding protects against COVID-19

Several studies have found severe acute respiratory syndrome coronavirus 2 (SARS-2) in breast milk after lactating women received two doses of messenger ribonucleic acid (mRNA)-based coronavirus disease 2019 (COVID-19). CoV-2) have been reported to exist. vaccination. More specifically, her IgG and IgA against SARS-CoV-2 spike protein It has been identified in breast milk following vaccination and infection.

Importantly, antibody dynamics differ based on either infection or vaccination. For example, IgG levels appear to increase after the second vaccination, while sIgA levels increase after SARS-CoV-2 infection.

Further information is needed on the duration and potency of antibody responses in breast milk after the second vaccination and the effects of hybrid immunity conferred by breakthrough infections in the Omicron era.

Young infants are at higher risk of severe COVID-19 and hospitalization than older children. So far, her COVID-19 vaccine has not been approved in the United States for infants under six months old. However, vaccination during pregnancy can provide some protection for the infant.

Nonetheless, data on symptoms and immune defenses occurring after infection and vaccination are limited in breastfed infants and lactating individuals. Therefore, more information is needed to determine protection against COVID-19 in vulnerable infants, levels of antibody transfer to infants, and persistence of anti-SARS-CoV-2 antibodies in breast milk after vaccination. is.

About research

new lancet In a preprint* study, anti-SARS-CoV-2 antibody levels in breast milk obtained from lactating individuals after 2 or 3 doses of COVID-19 vaccination and after breakthrough infection in vaccinated mothers is evaluated. To this end, the researchers analyzed both infant and maternal symptoms after vaccination or infection, and the duration and presence of passively transmitted antibodies in the saliva of breastfed infants. .

The current study included lactating or pregnant individuals who received the COVID-19 vaccine between December 2020 and April 2022. All participants answered questions about the infant’s and mother’s symptoms after each vaccination. In addition, study participants with a history of breakthrough infection also answered questions about infant and maternal symptoms after infection.

Milk samples were collected at six different time points: pre-vaccination, 2 post-dose, 3 pre-dose, 3 post-dose, 5 months post-dose and post-infection. In addition, maternal blood samples were collected at the same time points as breast milk collection.

An assessment of antibody persistence in the saliva of post-breastfeeding infants was performed by collecting saliva samples immediately after breastfeeding, 30 min, 60 min and before the next feeding session.

Paired breast milk and saliva samples were also collected on the day of infant collection. Finally, we measured her IgA and/or IgG in milk, blood, and saliva samples using an anti-spike enzyme-linked immunosorbent assay (ELISA) assay.

Survey results

A total of 33 lactating individuals who received two doses of the COVID-19 vaccine provided milk samples. Of these individuals, 26 received her third vaccination, of which 19 of her provided samples for antibody evaluation.

Of these 19 participants, 10 reported breakthrough infections during the Omicron wave. In addition, another 14 of her participants provided saliva and/or milk samples and infant saliva samples after the second or third vaccination.

No participants reported severe symptoms after the third vaccination. Common maternal symptoms included injection site pain, fatigue, or fatigue.

Fewer symptoms were reported after the third dose than after the second dose. rice field.

All infected infants exhibited at least one COVID-19 symptom, one of which required emergency department evaluation. Additionally, seven of her eight infants required consultation with a doctor for a diagnosis of COVID-19.

The average infant age is 8 months and not all were exclusively breastfed. Milk anti-spike antibodies were observed 6-8 months after the second vaccination.

Notably, antispike IgG levels in breast milk decreased significantly over time, whereas antispike IgA levels remained detectable after the second vaccination. After the third vaccination, IgG levels were higher than those reported after the second vaccination. However, the increase in IgA was not significant.

IgG and IgA levels decreased 5 months after the third vaccination. Individuals with a history of breakthrough infection had higher IgA levels in their breast milk compared to after the second and third vaccinations.

Furthermore, anti-spike IgA levels were higher in the plasma of lactating individuals after infection compared to after the third vaccination. The correlation between blood IgA levels and milk was stronger after infection than after the third vaccination.

A positive correlation was observed between anti-spike IgA and anti-spike IgG antibodies in breast milk and maternal saliva. Furthermore, anti-spike IgA levels were significantly higher than IgG over time in post-breastfed infant saliva.

Conclusion

A current study reported that antibody levels in breast milk increased after a second COVID-19 vaccination and were maintained for up to 8 months in some individuals. Her IgG levels also rise after the third vaccination, but the increase in IgA was more pronounced after breakthrough infection. Furthermore, IgA was found to be more stable in the mouth of infants after breastfeeding. This is essential for the protection of infants.

Nevertheless, more large-scale studies are needed to understand the exact role of mammary antibodies in protecting infants from COVID-19. Future vaccine development must also focus on the induction of milk IgA antibodies to enhance protection in nursing infants.

*Important Notices

Preprint of The Lancet / SSRN First Look We publish a non-peer-reviewed, preliminary scientific report and should not be taken as conclusive, to guide clinical practice/health-related actions, or to be treated as established information.