COVID-19 mRNA Vaccination in Lactation: Assessment of Adverse Events and Vaccine Related Antibodies in Mother-Infant Dyads

Front Immunol. 2021 Nov 3;12:777103. doi: 10.3389/fimmu.2021.777103. eCollection 2021.


Background: Data regarding symptoms in the lactating mother-infant dyad and their immune response to COVID-19 mRNA vaccination during lactation are needed to inform vaccination guidelines.

Methods: From a prospective cohort of 50 lactating individuals who received mRNA-based vaccines for COVID-19 (mRNA-1273 and BNT162b2), blood and milk samples were collected prior to first vaccination dose, immediately prior to 2nd dose, and 4-10 weeks after 2nd dose. Symptoms in mother and infant were assessed by detailed questionnaires. Anti-SARS-CoV-2 antibody levels in blood and milk were measured by Pylon 3D automated immunoassay and ELISA. In addition, vaccine-related PEGylated proteins in milk were measured by ELISA. Blood samples were collected from a subset of infants whose mothers received the vaccine during lactation (4-15 weeks after mothers' 2nd dose).

Results: No severe maternal or infant adverse events were reported in this cohort. Two mothers and two infants were diagnosed with COVID-19 during the study period before achieving full immune response. PEGylated proteins were not found at significant levels in milk after vaccination. After vaccination, levels of anti-SARS-CoV-2 IgG and IgM significantly increased in maternal plasma and there was significant transfer of anti-SARS-CoV-2-Receptor Binding Domain (anti-RBD) IgA and IgG antibodies to milk. Milk IgA levels after the 2nd dose were negatively associated with infant age. Anti-SARS-CoV-2 IgG antibodies were not detected in the plasma of infants whose mothers were vaccinated during lactation.

Conclusions: COVID-19 mRNA vaccines generate robust immune responses in plasma and milk of lactating individuals without severe adverse events reported.

Keywords: COVID-19; SARS-CoV-2; antibodies; breastfeeding; human milk; lactation; mRNA vaccine; passive immunity.

Publication types

  • Clinical Trial
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • 2019-nCoV Vaccine mRNA-1273
  • Adult
  • Antibodies, Viral / blood
  • Antibodies, Viral / immunology*
  • BNT162 Vaccine
  • COVID-19 / prevention & control
  • COVID-19 Vaccines / administration & dosage*
  • Female
  • Humans
  • Immunoglobulin A / immunology
  • Immunoglobulin G / blood
  • Immunoglobulin G / immunology
  • Immunoglobulin M / blood
  • Immunoglobulin M / immunology
  • Infant
  • Infant, Newborn
  • Lactation / immunology*
  • Male
  • Middle Aged
  • Milk, Human / immunology*
  • SARS-CoV-2 / immunology*


  • Antibodies, Viral
  • COVID-19 Vaccines
  • Immunoglobulin A
  • Immunoglobulin G
  • Immunoglobulin M
  • 2019-nCoV Vaccine mRNA-1273
  • BNT162 Vaccine