Quantification and Progress Over Time of Specific Antibodies Against Severe Acute Respiratory Syndrome Coronavirus 2 in Breast Milk of Lactating Women Vaccinated With BNT162b2 Pfizer-BioNTech Coronavirus Disease 2019 Vaccine (LacCOVID)

  1. Erika Esteve-Palau
  2. Araceli Gonzalez-Cuevas
  3. M Eugenia Guerrero
  4. Clara Garcia-Terol
  5. M Carmen Alvarez
  6. Geneva Garcia
  7. Encarna Moreno
  8. Francisco Medina
  9. David Casadevall
  10. Vicens Diaz-Brito

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Abstract

Background

Several observational studies demonstrated the passage of postvaccine antibodies through breast milk in women vaccinated against coronavirus disease 2019 (COVID-19), mostly with messenger RNA (mRNA)–based vaccines, but lacked long-term data.

Methods

A 6-month prospective cohort study was performed to determine severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine–induced antibody levels in the breast milk of 33 lactating healthcare workers at different timepoints after mRNA BNT162b2 Pfizer-BioNTech COVID-19 vaccination. Moreover, we examined the correlation of SARS-CoV-2 antibody levels between serum and breast milk, adverse events related to vaccination, and rate of SARS-CoV-2 infections.

Results

Mothers’ median age was 38 (interquartile range [IQR], 36–39) years and 15 (IQR, 10–22) months for infants. Median (IQR) SARS-CoV-2 immunoglobulin G (IgG) spike protein subunit S1 (S1) vaccine–induced levels at different timepoints for serum–milk pairs were 519 (234–937) to 1 (0–2.9) arbitrary units (AU)/mL at 2 weeks after first dose and 18 644 (9923–29 264) to 78 (33.7–128), 12 478 (6870–20 801) to 50.4 (24.3–104), 4094 (2413–8480) to 19.9 (10.8–51.9), 1350 (831–2298) to 8.9 (7.8–31.5) AU/mL at 2, 4, 12 and 24 weeks after second dose, respectively. We observed a positive correlation of antibody levels between serum and breast milk, no serious adverse events related to vaccination, and 2 (6%) COVID-19 vaccine breakthrough infections.

Conclusions

Women vaccinated with Pfizer-BioNTech transmit antibodies into breast milk with a positive correlation with serum levels. Both decreased over time in a 6-month follow-up.

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  1. Version published to 10.1093/ofid/ofac239
  2. Version published to 10.1101/2021.11.11.21266119v2 on medRxiv
  3. ScreenIT

    SciScore for 10.1101/2021.11.11.21266119: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    EthicsConsent: The study was explained to all volunteers in detail, and all gave written informed consent prior to participating.
    IRB: The Sant Joan de Déu Research Foundation ethics committee approved this study.
    Sex as a biological variableThe primary end-point was to determine SARS-CoV-2 vaccine induced antibody levels in the breast milk of lactating women 4 weeks after mRNA BNT162b2 Pfizer-BioNTech COVID-19 complete vaccination.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.

    Table 2: Resources

    Antibodies
    SentencesResources
    When blood samples were obtained, they were centrifuged for 15 minutes at 3,500 rpm and processed to determine levels of immunoglobulin (Ig) G antibodies against the spike protein S1 subunit (IgG-S1) and against the nucleocapsid (IgG-NC) of SARS-CoV-2 (Architect, Abbott®).
    S1 subunit (IgG-S1
    suggested: None
    Software and Algorithms
    SentencesResources
    Statistical analyses were performed with R version 4.0.3 (R Project for Statistical Computing), and figures created using ggplot2 R package.
    R Project for Statistical
    suggested: (R Project for Statistical Computing, RRID:SCR_001905)
    ggplot2
    suggested: (ggplot2, RRID:SCR_014601)

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

    Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
    The main limitation of this study is its small sample size. In our sample, there was only one infant of exclusive breastfeeding age (<6 months) so it was not possible to analyze whether there is a greater passage of antibodies to milk in this period compared to a longer postpartum period. Moreover, with a larger sample, we could confirm the correlation between antibody levels in serum and breast milk that we found and predict the levels in milk from a serum sample determination. Furthermore, the use of different techniques for the analysis of the two types of antibodies, IgG-NC and IgG-S1, can lead to a bias in the interpretation of the data. Most of the studies in pregnant and lactating women to date have been conducted after vaccination with mRNA vaccines. More studies with other vaccines are needed to be able to extrapolate these data to other types of vaccine. Finally, larger prospective studies are needed to confirm the safety of SARS-CoV-2 vaccination in individuals who are breastfeeding and further assess the association between vaccination and infants’ health and SARS-CoV-2 specific immunity.

    Results from TrialIdentifier: No clinical trial numbers were referenced.

    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.

    Results from JetFighter: We did not find any issues relating to colormaps.

    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • No protocol registration statement was detected.

    Results from scite Reference Check: We found no unreliable references.

    About SciScore

    SciScore is an automated tool that is designed to assist expert reviewers by finding and presenting formulaic information scattered throughout a paper in a standard, easy to digest format. SciScore checks for the presence and correctness of RRIDs (research resource identifiers), and for rigor criteria such as sex and investigator blinding. For details on the theoretical underpinning of rigor criteria and the tools shown here, including references cited, please follow this link.

  4. Version published to 10.1101/2021.11.11.21266119v1 on medRxiv