To the Editor:

We would like to begin our response by thanking Drs. Cosentino and Marino for their commentary regarding our recent publication, Detection of SARS-CoV-2 IgA and IgG in human milk and breastfeeding infant stool 6 months after maternal COVID-19 vaccination [1]. Our manuscript focused on mother/infant dyads wherein we assessed the durability of SARS-CoV-2 specific IgA and IgG antibody expression within human breast milk and plasma 6 months post first maternal mRNA COVID-19 vaccination. This, together with our evaluation seeking to identify the presence of such antibodies within the stool of breastfed infants.

We respectfully disagree with the term “flawed” in terms of our studies. Indeed, as noted in the manuscript’s prose, we were extremely careful in presenting the limitations of this study and in the wording of our conclusions. Our conclusions were also cautious in our recommendations that any findings should be confirmed in future studies.

In regard to specifics, due to the small sample size and unbalanced number of assessments, we did not adjust for multiple comparisons to reduce the potential for type II error. Instead, we attempted to present findings that may be of clinical relevance. Despite such limitations, which we freely noted, our pilot data demonstrates the clear expression of neutralizing SARS-CoV-2 specific antibodies within the breastmilk of vaccinated mothers, thereby suggesting a transfer of those antibodies from the milk to their infants.

Drs. Cosentino and Marino also state that “unintended exposure of infants to vaccine RNA and/or to the resulting S protein is at present a matter of concern,” which is based largely on an opinion article published by their group. With full respect to such, we would posit that speculation and conjecture regarding the production and clearance of the S protein after vaccination is beyond the scope of our article, one that focused on mother/infant dyads. However, it is well established that vaccination in pregnancy for the primary prevention of communicable diseases, like influenza or whooping cough, has proven one of the most effective public health interventions in recent decades, leading to significant reductions in maternal and perinatal morbidity and mortality [2]. Additionally, the INTERCOVID MULTINATIONAL COHORT STUDY, which includes thousands of pregnant women, demonstrated a consistent and substantial increase in severe maternal morbidity and mortality, and neonatal complications among symptomatic and unvaccinated women, initially with alpha and more recently with omicron as a variant of concern [3, 4]. Finally it has been shown that COVID-19 vaccination in pregnant and lactating individuals does not cause significant vaccine-related adverse events or obstetrical and neonatal outcomes, and is effective in preventing COVID-19 disease [5]. We hope and believe our publication will, over time, be seen as an important contribution to this evolving story regarding the impact of the COVID-19 pandemic on human health.