BNT162b2 vaccination induces SARS-CoV-2 specific antibody secretion into human milk with minimal transfer of vaccine mRNA

Abstract

Importance: To examine the impact of SARS-CoV-2 vaccination of lactating mothers on human milk Objective: (1) To quantify SARS-CoV-2-specific immunoglobulin A (IgA) and immunoglobulin G (IgG) in human milk of lactating mothers who received the BNT162b2 vaccine, with reference to a cohort convalescent from antenatal COVID-19, and healthy lactating mothers. (2) To detect and quantify vaccine mRNA in human milk after BNT162b2 vaccination. Design: Gestational Immunity For Transfer 2 (GIFT-2) is a prospective cohort study of lactating mothers who were due to receive two doses of BNT162b2 vaccine, recruited between 5th February 2021 and 9th February 2021. Setting: Lactating healthcare workers living in Singapore Participants: Convenience sample of ten lactating healthcare workers. Human milk samples were collected at four time points: pre-vaccination, 1 to 3 days after dose one, 7 to 10 days after dose one, and 3 to 7 days after dose two of the BNT162b2 vaccine. Exposure: Two doses of the BNT162b2 vaccine 21 days apart. Main Outcome and Measure: (i) SARS-CoV-2-specific IgA and IgG in human milk of lactating mothers who received BNT162b2 vaccine, (ii) Detection and quantification of vaccine mRNA in human milk after BNT162b2 vaccination. Results: Ten lactating healthcare workers aged 32.5 years (range 29 to 42) were recruited, with 40 human milk samples collected and analysed. SARS-CoV-2-specific IgA was predominant in human milk of lactating mothers who received BNT162b2 vaccine. The sharpest rise in antibody production was 3 to 7 days after dose two of the BNT162b2 vaccine, with medians of 1110 picomolar of anti-SARS-CoV-2 spike and 374 picomolar of anti-Receptor Binding Domain IgA. Vaccine mRNA was detected only on rare occasions, at a maximum concentration of 2 ng/mL. Infants had no reported adverse events, up to 28 days after ingestion of post-vaccination human milk. Conclusions and Relevance: In this cohort of ten lactating mothers following BNT162b2 vaccination, nine (90%) produced SARS-CoV-2 IgA, and ten (100%) produced IgG in human milk with minimal amounts of vaccine mRNA. Lactating individuals should continue breastfeeding in an uninterrupted manner after receiving mRNA vaccination for SARS-CoV-2.

COVID-19 mRNA Vaccination in Lactation: Assessment of adverse events and vaccine related antibodies in mother-infant dyads

“…It has recently been shown in a few studies that vaccine mRNA is not present in milk samples after vaccination (17,18), or is only detected in very low levels in some cases (19), providing reassurance that risks of exposure to the breastfed infant are minimal. This study adds to the evidence that vaccine components are minimally transferred to human milk.…”

“…Although mothers vaccinated during lactation transferred antibodies to their infant through milk, which is an important component of mucosal immunity for the baby, there was no passive transfer of antibodies to the infant bloodstream, as occurs if the mother is vaccinated during pregnancy. Correlates of infant immune protection to COVID- 19 are not yet well understood, however passive in utero transfer of IgG to the infant is important in the prevention of a number of infections including pertussis and influenza (24)(25)(26). Passively-transferred milk-derived IgA and IgG likely provide partial mucosal immune protection in infants, as breastfeeding is associated with lower risk of infections associated with mucosal defense, especially against respiratory infections (27)(28)(29).…”

Should we continue breastfeeding after SARS-CoV-2 infection or mRNA vaccination?

“…As we all know, IgG in breast milk has been shown to play a critical role in neonatal immunity against several other viral pathogens, including human immunodeficiency virus, influenza and respiratory syncytial virus (Fouda et al, 2011;Mazur et al, 2019;Demers-Mathieu et al, 2021b). By the way, the levels of Abs produced in breast milk after COVID-19 mRNA vaccination were significantly higher than those in the natural infection or convalescent period (Low et al, 2021a). Thus, even for lactating women who are naturally infected with COVID-19, vaccination may be helpful to induce and promote the transfer of anti-SARS-CoV-2 Abs in breast milk, as these protective Abs acquired after infection will weaken over time.…”

“…Therefore, breastfeeding has a low risk of transmitting SARS-CoV-2 and it can be continued under prudent precautions. Low et al (2021a) detected a very low level of vaccine mRNA using phenol-chloroform extraction, the gold standard for RNA extraction and double quencher qPCR probes (Low et al, 2021a). However, the discrepancies in the sensitivity of the detection method would lead to different test results.…”

“…To explore the safety of vaccination during breastfeeding, we conducted literature review using keywords "SARS-CoV-2, lactation, breast milk, breastfed, breastfeeding, mRNA vaccine" in Pubmed, Science Direct and Google Scholar database, and made Table 2 to summarize the symptoms of breastfeeding women who received the COVID-19 mRNA vaccine (Pfizer or Moderna) and adverse events in their children (Perl et al, 2021;McLaurin-Jiang et al, 2021;Low et al, 2021a;Golan et al, 2021c;Gray et al, 2021;Jakuszko et al, 2021;Low et al, 2021b;Selma-Royo et al, 2021;Lechosa-Muñiz et al, 2021;Low et al, 2021c). In terms of the symptoms in mothers after vaccination, following Dose 1, the frequency of specific symptoms such as pain, redness, joint or muscle pain at the injection site was not differed by vaccine brands.…”