Abstract
Objectives:
To investigate SARS-CoV-2 specific immunoglobulin A (sIgA) in breast milk of Thai mothers post COVID-19 vaccination and/or SARS-CoV-2 infection, and to compare the sIgA among lactating mothers with varying COVID-19 vaccination regimes.
Materials and Methods:
A longitudinal study was conducted in lactating mothers receiving ≥2 doses of COVID-19 vaccine or confirming SARS-CoV-2–positive test as a part of an infant feeding survey. Vaccination and infection details were collected through questionnaires and interviews. Self-collected breast milk samples (15 mL) at 1, 3, and 6 months postvaccination or infection were analyzed for sIgA through enzyme-linked immunosorbent assay (ELISA).
Results:
Eighty-eight lactating mothers (152 milk samples), average age of 30.7 ± 6.2 years, were recruited. Fifty-five percent of milk samples were from lactating mothers with both SARS-CoV-2 infection and vaccination (hybrid immunity); 40% were from those with vaccination alone (COVID naïve). Sixty percent of lactating mothers received mixed types of vaccines. Median sIgA ratio in breast milk was 2.67 (0.82–7.85). Breast milk sIgA at 1, 3, and 6 months were higher in mothers with hybrid immunity than in COVID naïve (geometric mean [95% confidence interval]: 3.30 [2.06–5.29] versus 1.04 [0.52–2.04], 3.39 [2.24–5.13] versus 1.26 [0.77–2.06], 4.29 [3.04–6.06] versus 1.33 [0.74–2.42], respectively). No significant differences were observed among various vaccination regimes.
Conclusion:
sIgA against SARS-CoV-2 was detected in breast milk for up to 6 months after immunization together with infection at a greater level than after immunization or infection alone. This immunity could be transferred and protective against SARS-CoV-2 infection. Discontinuation of breastfeeding among mothers who received COVID vaccination or experienced infection should be discouraged. Clinical Trial Registration number: TCTR20220215012.
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