Does Covid-19 and its vaccines adversely affect breast milk?

A health worker inoculates a mother, with her newborn baby beside her, with a dose of Covid-19 vaccine at a hospital in Chennai, India. Recent data indicates that antibodies from Covid-19 mRNA vaccines could pass through breastmilk, thus protecting babies as well. — AFP

The Covid-19 pandemic has affected all aspects of human life.

With babies still arriving in the world, a pertinent question posed by mothers or mothers-to-be revolve around the issue of breastfeeding with regards to Covid-19 vaccination and infection.

The World Health Organization (WHO) recommends that breastfeeding commence within an hour of birth, and be continued until the child is two years old or older as the benefits will continue for that long.

Multiple benefits

Breastfeeding benefits baby and mother.

However, only about a third of infants globally are exclusively breastfed for six months – a rate that has not changed in two decades.

Breast milk is the ideal food for infants.

Colostrum, which is the ideal first milk, helps the development of the infant’s digestive tract.

The only thing that may be deficient in breast milk is vitamin D, which can be easily remedied by maternal consumption of vitamin D drops.

Breast milk is safe and clean, and contains antibodies that protect against viruses and bacteria – a critical need in early life.

This is particularly so with colostrum, which has large amounts of immunoglobulin A (IgA) and other antibodies.

These antibodies are produced by mother, following exposure to viruses and bacteria, and will pass into the breast milk she produces.

Therefore, breastfeeding reduces baby’s risk of many infections.

Breast milk also provides all the energy and nutrient requirements of the infant’s first few months of life.

It continues to provide about half of such requirements during the second half of the first year of life and about a third during the second year of life.

Breast milk promotes healthy weight gain, while helping to prevent childhood obesity.

It has been reported that breastfeeding for more than four months leads to a significant reduction in baby being overweight and obese.

This has been attributed to higher amounts of beneficial gut bacteria, which may affect fat storage.

Breastfed babies also have more leptin, a hormone that regulates appetite and fat storage.

Breastfeeding has positive impact on babies’ long-term brain development.

Breastfed children do better in intelligence tests, and are less likely to develop behavioural problems and learning difficulties as they grow older.

The effects are most pronounced in preterm babies, who are more prone to developmental issues.

There are also significant benefits for the breastfeeding mother.

It helps in maternal-child bonding and in the regaining of pre-pregnancy weight as breastfeeding burns calories.

Breastfeeding promotes uterine contraction to its previous size (involution) through the production of oxytocin, a hormone that is increased during pregnancy, childbirth and breastfeeding.

Breastfeeding mothers generally have less blood loss and faster involution.

They are also less likely to develop postpartum depression (PPD), which can occur soon after childbirth.

Mothers with PPD are more likely to have problems with breastfeeding and have breastfed for a shorter duration.

In addition, breastfeeding reduces the risk of several diseases, including breast and ovarian cancer, high blood pressure, heart disease, type 2 diabetes, high blood lipids (fats) and arthritis.

Continued breastfeeding prevents ovulation and menstruation.

This may be nature’s way of ensuring a time lag between pregnancies.

However, it is important for breastfeeding mothers to use contraception no later than six months after childbirth, as the impact on ovulation wanes after that.

Covid-19 vaccines and breastfeeding

The evidence about the safety and effectiveness of Covid-19 vaccination during pregnancy has been growing, with the data suggesting that its benefits outweigh any known or potential risks.

Reports from clinical trials of Covid-19 vaccines currently in use did not include breastfeeding mothers.

As such, there is limited data on the safety of the vaccines in breastfeeding mothers, the effects on the breastfed baby, and the effects on milk production or excretion.

However, we can fall back on basic virology principles.

The mRNA (messenger ribonucleic acid) vaccines (e.g. from Pfizer/BioNTech), vector-based vaccines (e.g. from AstraZeneca/Oxford) and inactivated vaccines (e.g. from Sinovac) do not cause infection in recipients, including mother and baby.

These vaccines are effective in reducing the risks of severe disease, hospitalisation and death, and indirectly, prevent the spread of Covid-19.

As such, based on virology principles, Covid-19 vaccines are not contraindicated among pregnant or breastfeeding mothers.

Recent reports have shown that breastfeeding mothers who received the mRNA Covid-19 vaccines have antibodies in their breast milk that could protect their babies.

However, more data is needed to determine the protection these antibodies may provide to babies.

Current data also suggests that mRNA vaccines are preferred for breastfeeding mothers.

Vector-based vaccines can be considered if there is no access to mRNA vaccines.

In general, live vaccines are contraindicated in pregnancy and breastfeeding, although none of the current Covid-19 vaccines are live.

The jury is still out on the mixing of various types of vaccines and intervals.

Until further evidence is available, it is good clinical practice to administer similar types of vaccine to the individual, especially the pregnant and breastfeeding.

Covid-19 and breastfeeding

The current guidelines from WHO, the United Nations International Children’s Emergency Fund (Unicef), the US Centres for Disease Control and Prevention (CDC) and professional organisations have, to date, recommended continued breastfeeding even if the mother has Covid-19.

Their basis is the overall short- and long-term immunological and psychological benefits of breastfeeding.

There is understandable insecurity regarding the safety of the infants of Covid-19 mothers, and the advantages and disadvantages of discontinuing breastfeeding.

However, the regulators’ and professionals’ recommendations state that there is currently insufficient evidence of Covid-19 transmission through breastfeeding.

As such, strict mother-infant separation and discontinuation of breastfeeding are to be avoided, regardless of a positive diagnosis and intensity of symptoms.

If the mother is too ill to take care of the infant, expressed fresh and unpasteurised breast milk should be fed to baby.

In a review titled "Breastfeeding and COVID-19: From Nutrition to Immunity", published on April 7 (2021) in the Frontiers in Immunology journal, scientists said: “The most abundant antibody in breastmilk – sIgA – provides adequate specific protection against pathogens, among which are also viruses.

“The specificity of sIgA is determined by the immune response of the mother to previous infection, probably explaining the low rates of infection or milder symptoms of the infected breastfed infants of SARS-CoV–infected mothers.

“Further investigation is needed to accumulate knowledge regarding anti-SARS-CoV sIgA produced through breastfeeding for the neonate.”

If you are a breastfeeding mother who has caught Covid-19 and have any doubts about continuing breastfeeding, do discuss the matter with your attending doctors.

Dr Milton Lum is a past president of the Federation of Private Medical Practitioners Associations and the Malaysian Medical Association. For more information, email [e-mail]. The views expressed do not represent that of organisations that the writer is associated with. The information provided is for educational and communication purposes only and it should not be construed as personal medical advice. Information published in this article is not intended to replace, supplant or augment a consultation with a health professional regarding the reader’s own medical care. The Star disclaims all responsibility for any losses, damage to property or personal injury suffered directly or indirectly from reliance on such information.