With over one billion COVID-19 vaccine doses administered to date, the world has experienced the most vast, unprecedented mass vaccination program in history in response to the onset of the SARS-CoV-2 outbreak, the worst pandemic in modern history. Known as COVID-19, the vaccine producers fell into geopolitical categories of the West (e.g. USA, Europe, Australia) and East (China and Russia), and in both cases, the experimental products were produced at historically breakneck speed. Of course, this unprecedented development both provided promise and shook nerves as in the case of the mRNA-based vaccines, these wholly different, more advanced, novel types of life-science-based technologies raised hope and stirred some fear. The two mRNA-based vaccines, both under U.S. Food and Drug Administration (FDA)-based emergency use authorization (EUA) in America, include BNT162b2 produced by BioNTech in partnership with Pfizer and mRNA-1273 developed by Moderna. With the emergency use authorization, many questions remained, such as whether they were safe for lactating women. The American College of Obstetrics and Gynecology and The Society for Maternal-Fetal Medicine both came out supporting the use on breastfeeding women but clinical trial protocols precluded this participant cohort. Questions about safety were high on mind. One U.S. study looked into issues involving administration of the mRNA-based vaccines in 31 breastfeeding women and found that 67% experienced side effects after dose one and 61% after dose two of the vaccine. This was a small sample, and so a recent study led by three researchers from University of California, San Diego, Department of Pediatrics, sought to better understand the impacts of these vaccines in this participant cohort—this most recent study involved 180 participants.
The Gary Study
In another study involving 31 breastfeeding moms (Gary KJ, Bordt EA, Atyeo C, et. al.) titled “COVID-19 vaccine response in pregnant and lactating women: a cohort study,” the authors led by Kathryn Gary out of Brigham and Women’s Hospital, Harvard Medical School, concluded that while the COVID-19 mRNA-based vaccines produced solid humoral immunity in pregnant and lactating women—similar immunogenicity and reactogenicity to those observed in non-pregnant women—they found, “Vaccine-induced immune responses were significantly greater than the response to natural infection.” They reported that actual transfer of the immune response to newborns was done via placenta and breastmilk.
This most recent UCSD study was recently uploaded to the medRxiv preprint server and hasn’t been peer reviewed as of yet.
UCSD Department of Pediatrics
This study was led by corresponding author and research manager for UCSD’s Department of Pediatrics, Division of Dysmorphology and Teratology, Kerri Bertrand, MPH, as well as two other colleagues from the department. The study was designed by Ms. Bertrand and Dr. Christina Chambers while the final statistical analysis was conducted by Gordon Honerkamp-Smith. The study was funded by the university as well as a grant from NIH-NICHD.
In the study, the group studied 180 breastfeeding women who received either the Pfizer/BioNTech or Moderna vaccines between December 14, 2020 and February 1, 2021 as part of the Mommy’s Milk Human Milk Research Biorepository initiative at UCSD.
A majority of the study participants were actively breastfeeding their babies with the mean age of the baby during the study at 7.47 months. 71.1% of the participants actually received BNT162b2 (Pfizer) while 28.9% received mRNA-1273 (Moderna). Interestingly, the researchers observed frequencies of reactionary symptoms that were similar across the two emergency use authorized products.
>85% of study participants reported side effects in the form of local or systemic symptoms for both vaccines following both the first and second doses.
Of interest, the second dose associated with mRNA-1273 (Moderna) triggered more systemic side effects from flu-like symptoms, such as muscle aches, chills, and fever to vomiting as well as localized symptoms, such as pain at the point of the jab.
Concerns with diminution of milk supply did surface with a reduction (8% vs 23.4%) for Pfizer and Moderna respectively post the second jab however apparently the milk yield normalized after 72 hours.
In what is claimed to be the very first study investigating mRNA-based vaccine outcomes in breastfeeding children, the study results did observe certain behavioral modifications in the children. These included irritability, erratic sleep and greater drowsiness observed for the children whose moms were administered with BNT162b2 (Pfizer/BioNTech).
Far Greater number of Side Effects
Post-vaccination side effects in this recent study uploaded to the preprint server medRxiv revealed a significantly higher percentage of lactating women reporting post-vaccination side effects in the form of both systemic and local symptoms. While they suggested a few different hypotheses (e.g. difference in methods of assessment, timing issues, etc.) the UCSD research team could not identify why this is the case. The authors reported:
“We found >85% of participants reported any symptoms for both the Pfizer-BioNTech and 94 Moderna vaccines following either dose. This is substantially higher than the 61-67% of women who reported any symptom in the Gray et al. paper.”
Is this Study Sufficient to Declare Conclusive Safety?
TrialSite believes considerable more study needs to occur in association with this vulnerable population. While this study provides some information involving safety of the novel mRNA-based vaccines administered on breastfeeding moms, and does add to the small numbers of total subjects involved with such study, it doesn’t offer any long-term intelligence into the true impact of these vaccines under use via EUA. More studies are needed and some are currently in process such as ones investigating the composition of milk as well as antibody samples in this study.
The investigators were pleased with the results, declaring, “These data are reassuring regarding the safety of vaccination in breastfeeding women and 106 of their breastfed children with either of the mRNA COVID-19 vaccines. Additional studies are 107 underway to evaluate milk composition and antibody status in samples obtained from women 108 participating in the current study.”
What is the Mommy’s Milk Human Milk Research Biorepository initiative at UCSD?
Located at the Center for Better Beginning, this biorepository is actually part of what is one of North America’s foremost institutes for breakthrough research and education in maternal health and child development. The team includes world-renowned medical professionals and researchers and a dedicated staff. Run within UCSD’s Department of Pediatrics, the Center houses and supports multiple programs and studies.
Dr. Chambers receives funding from Amge, AstraZeneca, Celgene, GSK, Janssen and Pfizer; Regeneron; Hoffman La-Roche-Genentech; Genzyme Sanofi-Aventis; Takeda Pharmaceutical Company Limited; Sanofi; UCB Pharma, USA; Sun Pharma Global FZE; Gilead; and the Gerber Foundation.
Gordon Honerkamp-Smith, C.Phil Statistics
Call to Action: TrialSite will continue to monitor studies tracking impact of vaccines on vulnerable populations.