Flawed evidence for maternal milk-derived SARS-CoV-2 IgA and IgG in breastfeeding infant stool after maternal COVID-19 vaccination
Our comment on a recently published study
On 12 January 2023, The Journal of Perinatology (Springer Nature) published a study entitled “Detection of SARS-CoV-2 IgA and IgG in human milk and breastfeeding infant stool 6 months after maternal COVID-19 vaccination”.
The study employed a prospective observational design and included 37 mothers and 25 infants. All mothers received COVID-19 vaccines during lactation except three, which were vaccinated during pregnancy. Milk, maternal plasma, and infants’ stool was collected pre-vaccination and up to 6 months following COVID-19 vaccination. SARS-CoV-2 antibody levels and their neutralization capacities were assessed. Three mothers/infants were excluded from the final analysis (1 mother stopped breastfeeding prior to first vaccination; and two mothers received the J&J vaccine, which - according to the authors - induced a significantly different antibody response). Results therefore refer only to mothers vaccinated with COVID-19 mRNA vaccines.
According to the authors, results show that SARS-CoV-2-specific IgA and IgG levels were 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 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 is in the very same range in infants milk-fed by vaccinated mothers and in controls.
In addition, the correlation between infant stool IgG and maternal plasma and milk IgG (Supplemental 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 neither any improvement in infants’ stool SARS-CoV-2 specific neutralization capacity following maternal SARS-CoV-2 vaccination, as stated instead in the discussion, except possibly for the small subgroup of infants with high stool IgG levels, which however it 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 the milk-fed infants. This is even more important in the light of available evidence showing the occurrence of vaccine-derived SARS-CoV-2 Spike (S) protein mRNA in the milk of women after administration of COVID-19 vaccines [1,2]. 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 [3,4]), 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 [5]. 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.
We expressed our concern in a Letter to the Editor of The Journal of Perinatology, which underwent peer review and is now accepted for publication.
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;176:1268-1270.
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;28:542-554.
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;325:2013-2014.