Protection against COVID-19 is important for the health of infants and children. As of November 2021, 6.9 million children have tested positive for COVID-19, with up to 1.9% of those requiring hospitalization and up to 0.3% resulting in death.1 While COVID-19 infection is often mild in children, those younger than 2 years may be more likely to be severely affected and passive immunity from breastfeeding may be an important way to protect this vulnerable population.2 Vaccinating lactating individuals has historically provided protection to their infants from diseases such as rotavirus, influenza, and pertussis.3 Unfortunately, the initial large manufacturer trials for COVID-19 vaccination did not include lactating individuals. Thus, there was an initial dearth of information regarding the risks and benefits in this population, emphasizing the urgent need to study the potential effects of COVID-19 vaccination in lactating individuals and whether vaccination could provide protection to their breastfeeding infants. While numerous studies have subsequently been published regarding the effect of vaccination in lactating individuals, the initial lack of information created confusion and concern regarding the safety of vaccination while lactating and delayed vaccination in this population. Currently, vaccination of lactating individuals is recommended by numerous national and international organizations including the Academy of Breastfeeding Medicine, the American Colleges of Obstetricians and Gynecologists, and the Centers for Disease Control and Prevention. However, lactating individuals continue to express concern regarding vaccination safety and the potential effect on lactation and infant health.4,5

Multiple studies have subsequently reported passage of anti-SARS-CoV-2-specific IgG and IgA with the ability to neutralize the SARS-CoV-2 virus into breast milk following vaccination.5-7 These antibodies are found following the first vaccination dose, increase further after the second, are higher than after COVID-19 infection, and are consistent with the increase in concentration found in the lactating individual's blood.8 While these antibodies have been shown to neutralize the SARS-COV-2 virus in vitro, it is less clear to what extent they protect the breastfeeding infant from infection.

The risk for potential harm to the lactating infant following vaccination is a frequently expressed concern of lactating individuals.4,5 However, the possibility that the vaccine would enter the individual's bloodstream and reach the breast is minimal and it is even less likely that the intact nanoparticle or mRNA would be transferred to the milk. Furthermore, if transferred into the milk, these elements would be easily digested by the infant and thus adverse events are unlikely. Multiple studies have shown that the mRNA is not found in breast milk,9,10 nor the infant's blood,11 following COVID-19 vaccination. Finally, no serious adverse events in lactating infants have been reported in the literature while a few minor effects including fever, irritability, poor sleep, drowsiness, reduced feeding frequency, and gastrointestinal symptoms have been found.6,12 These minor symptoms vary on the basis of the type of vaccine administered and may be more prevalent after the second dose.11 A large study of 4455 lactating individuals found 7.1% reported minor reactions in their infants.13 It is not known whether these events are directly caused by the vaccine, and several studies have failed to find any negative effect in lactating infants.14

Lactating individuals have also expressed concern regarding the potential negative effect of COVID-19 vaccination on lactation.4,5 The majority of studies indicate minimal risk to milk production.13,14 However, some women notice a temporary reduction in supply while others report a small increase.12,13 The previously cited survey of 4455 lactating individuals found 6% reported a decrease and 3.9% reported an increase in milk production, which were more likely after the second dose.13 However, these studies were not specifically focused on parents of infants in the neonatal intensive care unit who may be at a substantial risk of suboptimal milk production.

As nurses, it is likely that we will be called upon to counsel lactating individuals regarding COVID-19 vaccination and our actions may have long-lasting consequences. We must be prepared to provide parents the most recent evidence-based information on which to base their decision. Furthermore, providing this information in a safe and nonjudgmental environment that encourages individual questions is essential. Understanding the reasons that influence acceptance or refusal of vaccines is important for developing targeted and personalized communication.

Based upon the available literature, it appears the vaccine likely has minimal detrimental effects on lactating individuals and their infants. However, the failure of vaccine manufacturers to include data for the more than 100 million lactating individuals worldwide has been a detriment to our ability to council the families that we care for. The significant delay in information regarding the risk and benefit of vaccination in lactating individuals resulted in many electing to discard their milk after vaccination or to cease breastfeeding altogether, neither of which supports the lactating dyad. Thus, it is imperative that manufacturers consider the effect of vaccination on lactating individuals and their infants.

-Leslie A. Parker, PhD, APRN, FAANP, FAAN

College of Nursing

University of Florida

Gainesville, FL

References