New Research on Breast Milk, Breastfeeding, and COVID-19

Breastfeeding and COVID-19: What to Know

Important research in COVID transmission and the response in human breast milk is just beginning, but studies are starting to be published. Recently, two studies were published coming from both coasts - one from Mt. Sinai in New York and the other from the University of California San Diego. The Mt. Sinai study, published in May 2020, examined the human milk immune response to SARS-CoV-2. The University of Californa study, published in August 2020, published initial findings detailing whether or not SARS-CoV-2 could be transmitted by breastfeeding. While both of these studies are recently published since the pandemic began and more research is needed (and will be done!), these two initial studies show interesting and significant findings.

See below for brief reviews of each study (with links to the actual published study for more information):

First Study (Mt. Sinai Examination of Human Milk Response to SARS-CoV-2)

The Mt. Sinai study, completed by Rebecca Powell et al, is titled Evidence of a Significant Secretory IgA-Dominant SARS-CoV-2 Immune Response in Human Milk Following Recovery from COVID-19. It's a long title, but what they looked at was the antibody response in human milk - with specific examination of the antibody IgA (secretory IgA), or the antibody from lymphoid mucosa. The researchers wanted to know the extent of human milk response to SARS-CoV-2 (coronavirus). They discussed how infants and children tend to not suffer greatly from COVID-19, but are likely responsible for transmission of the virus. They also felt that if human milk antibodies could be purified and used as a COVID-19 therapeutic, they would likely be of the secretory class (secretory IgA). 

15 milk samples were obtained from donors previously infected with SARS-CoV-2, as well as 10 negative control samples (from donors prior to December 2019). Approximately 30 ml of milk was obtained from each of the participants using an electric or manual breast pump. Milk was obtained 14 - 30 days after symptoms abated. 

Overall, the data indicated that there is a strong IgA response in human milk after the majority of individuals in this study were infected. They could not determine from this study if it was secretory IgA.

With that in mind, the authors acknowledge that more studies are necessary and "the magnitude, functionality, and durability of the human milk immune response to SARS-CoV-2 reactive milk antibodies must be comprehensively studied for potential therapeutic and protective efficacy." As of this writing, they are continuing this important study and have since recruited over 1,000 lactating participants, including 350 who have recovered from SARS-CoV-2. 

Second Study (University of California Examination of Human Milk Transmission Via Breast Milk)

The second study, out of the University of California, was completed by Christina Chambers, Ph.D., MPH et al, and is a research letter published in the AMA on August 19, 2020. It is titled Evaluation for SARS-CoV-2 in Breast Milk from 18 Infected Women.

This study acknowledges the concern that COVID-19 may be transmitted to infants by breastfeeding but, as of this publication date, there has been no documented case that the virus has occurred through breast milk. The researchers also acknowledge that the detection of viral RNA does not equate with infectivity, but the potential for viral transmission through breast milk is a vital, crucial question for women who wish to breastfeed but test positive for COVID-19.

The researchers enrolled 18 women who had a confirmed SARS-CoV-2 infection. These women provided between 1 - 12 samples of breast milk, with a total of 64 samples collected and to be tested. They also added SARS-CoV-2 to 2 milk samples from 2 different control donors, whose milk was provided prior to the pandemic. They then mimicked the conditions of Holder pasteurization (used in milk banks) on these samples.

The results showed that one sample had detectable SARS-CoV-2 RNA but "no replication-competant virus was detectable in any sample, including the sample that tested positive for viral RNA." This means that no RNA was found that could replicate or cause disease. For the 2 samples of control milk with SARS-CoV-2 added and then Holder pasteurized, RNA was not detected nor was culturable virus detected.

The findings were reassuring, though the authors realize the limitations of the sample size and some protocols.

The virus has caused much disruption across the globe and in every area of life, including the newborn and how that infant is fed. The COVID-19 virus is still in the early stages of entering our world and, as of this writing, it has only been about 6 months since the virus was called a pandemic and life for everyone changed. However, it is important that research is being done and published so we can have some idea of how the virus can affect the newborn through human milk and breastfeeding. More research is necessary (and is being done), but it's important to look at these early studies to help make informed, educated decisions based on science and clinical evidence. 

Lastly, to my colleagues on the frontlines of this pandemic: I am so proud of all of you!