COVID-19 Vaccination,Breastfeeding,and Milk Supply

Dear Editor:

We would like to share ideas on publication “Maternal and Child Outcomes Reported by Breastfeeding Women Following Messenger RNA COVID-19 Vaccination.” ¹ Bertrand et al. mentioned that “A small proportion of women following the first dose of either vaccine brand reported a reduction in milk supply ¹ ”and noted a reduction of milk supply was more common following the second dose of vaccine. ¹ “Can COVID-19 vaccination affect the milk volume?” is an interesting question. After COVID-19 vaccination, the blood viscosity of the mother increases. ²

According to the previous report, the highest increasing level of blood viscosity occurs after the administration of the second dose of COVID-19 vaccine. ² An increased blood viscosity might affect milk supply. In the mother with a known medical condition with increased blood viscosity, such as diabetes, a reduction in milk supply is reported. ³ Hence, a reduction in milk supply reported by some mothers is possible.