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New Study Shows J&J Offers Lowest Chance of Antibodies in Breast Milk

woman getting a vaccine


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Key Takeaways

  • Vaccinated breastfeeding women can pass protective antibodies to their babies through their breast milk.
  • A recent study, which is not yet peer-reviewed, found lower levels of antibodies in moms who had received the Johnson & Johnson vaccine.
  • Doctors question whether these results are conclusive enough to recommend one type of vaccine over another for breastfeeding moms.

Breastfeeding moms who get the COVID-19 vaccine have antibodies in their milk, which may help protect their babies from a severe illness from the virus. And now we have an idea of which vaccines offer the most protection, thanks to a team led by Rebecca Powell, PhD, a human milk immunologist at New York’s Icahn School of Medicine at Mount Sinai.

The researchers studied the human milk immune response to vaccination. This research involved testing samples of breast milk from donors who received either the Moderna, Pfizer, or Johnson & Johnson vaccine, all of which have been granted emergency use authorization from the Food and Drug Administration (FDA). The Pfizer vaccine was recently granted full approval by the FDA.

About the Study

Dr. Powell and her team examined COVID-19 neutralizing antibody levels in breast milk right before the donors received the vaccine and again during the peak antibody time period after receiving the vaccine. For Moderna and Pfizer, both mRNA vaccines, the peak comes 14 days after the second dose. Johnson & Johnson is a traditional, single-dose vaccine, and its peak occurs 28 days after the shot. 

Three types of antibodies were analyzed in the study. These antibodies included immunoglobulin G (IgG), immunoglobulin A (IgA), and secretory immunoglobulin A antibodies (sIgA).

IgG is the most abundant antibody found in blood and the main antibody produced in breast milk following the COVID-19 vaccines. Meanwhile, IgA is the most abundant antibody naturally present in breast milk; and sIgA, which plays a critical role in the immune function of mucus membranes, is the most durable of the three antibodies in breast milk due to its protective protein shell.

Rebecca Powell, PhD

Johnson & Johnson is not a good option for breastfeeding moms. But if that’s all you have, it is still better than nothing.

— Rebecca Powell, PhD

The findings, which haven’t yet been peer-reviewed, are published in Allergy and Immunology. They reveal that 100% of the participants who got the Moderna or Pfizer vaccines made vaccine-induced IgG in their milk, but only 62% of those who received the Johnson & Johnson vaccine appeared to have any vaccine-induced IgG in their breast milk.

Also, those who got the Johnson & Johnson vaccine who did produce IgG produced considerably lower levels of those antibodies than those who received the Moderna or Pfizer vaccines. In terms of IgA production, the Moderna vaccine came out on top.

Donors who received this vaccine produced the highest amounts of this antibody in their breast milk. Additionally, 25% more Moderna recipients showed an increase in sIgA production in breast milk compared to their Pfizer or Johnson & Johnson counterparts. The bottom line from the researchers?

“Johnson & Johnson is not a good option for breastfeeding moms,” Dr. Powell says. “But if that’s all you have, it is still better than nothing.”

What Do Doctors Think?

Randy Fiorentino, MD, an OB/GYN at Providence St. Joseph Hospital in Orange County, California, isn’t surprised by the findings. 

“The Johnson & Johnson vaccine has also been shown to induce less antibody response and is slightly less effective in preventing moderate to severe disease,” he says.

However, he points out that there has been enough data showing antibody levels in breast milk to support the use of this particular vaccine in pregnant and lactating women. Plus, research into antibody protection in breast milk is still ongoing. 

“The study shows antibody levels in the breast milk of recipients of each type of vaccine, and merely less in the breast milk of lactating women who received the Johnson & Johnson vaccine,” Dr. Fiorentino says. “This alone should not preclude its use in pregnant or lactating women.” 

Supriya Narasimhan, MD, MS, division chief of infectious diseases at Santa Clara Valley Medical Center in San Jose, California, agrees that the recent paper highlights the need for further research with larger sample sizes.

Supriya Narasimhan, MD, MS

I would strongly encourage all pregnant and breastfeeding mothers to protect themselves by vaccination as a means of protecting their newborns.

— Supriya Narasimhan, MD, MS

Dr. Narasimhan also doesn’t think the data is conclusive enough to recommend one vaccine over another for a breastfeeding mother. There is a great deal of variation in the immunoglobulin profile of breast milk in general, she says.

“The sample sizes in this study are small and the Moderna and Pfizer post-vaccination samples are closer to 5 to 6 weeks whereas Johnson & Johnson was closer to 4 weeks post-vaccination,” she says. “It is unclear if this attributed to a difference in the breast milk antibody profile.”

She adds that the biggest risk factor for COVID-19 exposure to the newborn is COVID-19 infection in the mother and the immediate family. So, families need to get vaccinated to protect newborns.

“Protection of the family members including the mother is paramount in preventing COVID-19 infection of the newborn,” she says. “I would strongly encourage all pregnant and breastfeeding mothers to protect themselves by vaccination as a means of protecting their newborn.” 

Remember, both the Centers for Disease Control and Prevention (CDC) and the American College of Obstetricians and Gynecologists (ACOG) indicate that there is no overriding reason for a pregnant or breastfeeding woman to avoid getting the COVID-19 vaccine.

What This Means For You

While antibodies delivered through breast milk don’t give babies 100% immunity to COVID-19 and other viruses, they do help reduce the risk of severe illness and transmission of the virus. If you are offered the COVID-19 vaccine while you’re breastfeeding you may want to consider getting vaccinated. Talk to your healthcare provider about what is right for you.

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Article Sources
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  1. Fox A, DeCarlo C, Yang X, Norris C, Powell RL. Comparative profiles of SARS-CoV-2 spike-specific milk antibodies elicited by COVID-19 vaccines currently authorized in the USA. MedRxiv. Preprint posted online July 23, 2021. doi:10.1101/2021.07.19.21260794

  2. Centers for Disease Control and Prevention. COVID-19 vaccines while pregnant or breastfeeding. Updated August 11, 2021.

  3. American College of Obstetricians and Gynecologists. Coronavirus (COVID-19), pregnancy, and breastfeeding: a message for patients. Updated August 4, 2021.