To the Editor:
Secretion of neutralizing SARS-CoV-2 IgA and IgG in human milk after vaccination against COVID-19 is well established [1]. Little however is known so far about IgA and IgG transfer from milk to breastfeeding infants and its clinical relevance. A recent paper published in this Journal [2] addresses the issue by investigating SARS-CoV-2 IgA and IgG, and their SARS-CoV-2 neutralization capacities, in maternal milk and plasma before and after COVID-19 vaccination, as well as in infants’ stool [2]. Based on their data, the authors conclude that SARS-CoV-2-specific IgA and IgG levels and SARS-CoV-2 neutralization capacity are higher in infant stool post-maternal vaccination amongst milk-fed compared to controls. Careful examination of reported results leads however to different conclusions.
Figure 1 of the paper [2] clearly shows that stool neutralization capacity and IgA levels are not different between infants milk-fed by vaccinated mothers in comparison to controls, as also indicated by the reported P values of respectively 0.8 and 0.08, the latter likely due to a single outlier value in the group of infants milk-fed by vaccinated mothers. The difference in IgG levels, although statistically significant, is due just to a minor subgroup of subjects with slightly higher values among infants milk-fed by vaccinated mothers, while the majority of values are in the very same range in infants milk-fed by vaccinated mothers and in controls. The correlation between infant stool IgG and maternal plasma and milk IgG (Supplementary Table 2) obtained from 19 different analyses should be re-examined after adjustments for multiple comparisons.
In summary, study data clearly do not support any presence of specific SARS-CoV-2 antibodies in breastfeeding infants’ stool nor any improvement in infants’ stool SARS-CoV-2-specific neutralization capacity following maternal SARS-CoV-2 vaccination, as stated instead in the discussion [2], except possibly for the small subgroup of infants with high stool IgG levels, which however is unclear to what extent might result in any neutralization capacity.
As a whole, data presentation and interpretation are affected by irremediable mistakes, which misrepresent the consequences of maternal COVID-19 vaccination for milk-fed infants. This is even more important in light of available evidence showing the occurrence of vaccine-derived SARS-CoV-2 Spike (S) protein mRNA in the milk of women after the administration of COVID-19 vaccines [3, 4]. Increasing evidence points to a major contribution of vaccination-induced excessive production of S protein (and possibly of the vaccine RNA itself) in adverse effects following vaccination (reviewed in [5, 6]); thus, unintended exposure of infants to vaccine RNA and/or to the resulting S protein is at present a matter of concern. Remarkably, reports exist showing that some infants milk-fed by COVID-19-vaccinated women experience fever early after maternal vaccination [7]. Whether fever is a consequence of exposure to vaccine RNA and/or to the S protein remains to be established; however, the possibility should not be ignored in view of its critical importance for the safety assessment of COVID-19 vaccinations in breastfeeding women.
References
Whited N, Cervantes J. Antibodies against SARS-CoV-2 in human breast milk after vaccination: a systematic review and meta-analysis. Breastfeed Med. 2022;17:475–83.
Stafford LS, Valcarce V, Henry M, Neu J, Parker L, Mueller M, et al. Detection of SARS-CoV-2 IgA and IgG in human milk and breastfeeding infant stool 6 months after maternal COVID-19 vaccination. J Perinatol. 2023; https://doi.org/10.1038/s41372-022-01581-5.
Yeo KT, Chia WN, Tan CW, Ong C, Yeo JG, Zhang J, et al. Neutralizing activity and SARS-CoV-2 vaccine mRNA persistence in serum and breastmilk after BNT162b2 vaccination in lactating women. Front Immunol. 2022;12:783975.
Hanna N, Heffes-Doon A, Lin X, Manzano De Mejia C, Botros B, Gurzenda E, et al. Detection of messenger RNA COVID-19 vaccines in human breast milk. JAMA Pediatr. 2022;176:1268–70.
Cosentino M, Marino F. Understanding the pharmacology of COVID-19 mRNA vaccines: playing dice with the spike? Int J Mol Sci. 2022;23:10881.
Trougakos IP, Terpos E, Alexopoulos H, Politou M, Paraskevis D, Scorilas A, et al. Adverse effects of COVID-19 mRNA vaccines: the spike hypothesis. Trends Mol Med. 2022;28:542–54.
Perl SH, Uzan-Yulzari A, Klainer H, Asiskovich L, Youngster M, Rinott E, et al. SARS-CoV-2-specific antibodies in breast milk after COVID-19 vaccination of breastfeeding women. JAMA. 2021;325:2013–4.
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MC and FM contributed equally to the conception and drafting of the manuscript, which they unanimously approved in its final version and for whose integrity they assume full responsibility.
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Cosentino, M., Marino, F. In response to Detection of SARS-CoV-2 IgA and IgG in human milk and breastfeeding infant stool 6 months after maternal COVID-19 vaccination. J Perinatol 43, 827 (2023). https://doi.org/10.1038/s41372-023-01669-6
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DOI: https://doi.org/10.1038/s41372-023-01669-6
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