Background: The COVID-19 pandemic was controlled by mass vaccination of the population of all countries throughout the world. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) affected both pregnant and lactating mothers equally. The objectives of the study were to provide information on vaccine-induced breast milk antibody immunoglobulin (Ig) A and IgG response in the serum of mothers and to observe the persistence of these antibodies postvaccination at different periods in lactating women.
Materials and methods: The study is a longitudinal, prospective, monocentric study in a tertiary care hospital for the duration of 1 year from March 2022 to 2023. A total of 150 blood and 150 breast milk samples were collected from 50 participants at three different intervals. The samples were collected within 1 week (T1), 6 weeks (T2), and 6 months (T3) from delivery. SARS-CoV-2 specific IgA antibody was detected by enzyme-linked immunosorbent assay (ELISA) using a COVID-19 human IgA ELISA kit from Raybio. ELISA detected SARS-CoV-2 specific IgG antibody using the access SARS-CoV-2 IgG assay.
Results: The mean serum concentration of SARS-CoV-2 receptor binding domain-specific IgG (RBD-S-IgG) antibodies [signal-to-cutoff ratio (S/CO)] in vaccinated individuals were 5.35 (6.26), 9.80 (10.68) and 6.89 (8.93) in 1st week, 6th week, and 6th month, respectively. The mean breast milk concentration of SARS-CoV-2 RBD-S-IgA antibodies (units/mL) was 75.93 (106.19), 109.02 (150.50), and 318.23 (443.82) in 1st week, 6th week, and 6th month respectively. Around 78% of study participants had anti-SARS-CoV-2 IgG in their serum, and 88% of them had anti-SARS-CoV-2 IgA in their milk at 1st week.
Conclusion: Postvaccination, breastfeeding should be encouraged in lactating mothers, as it will have the additional benefit of providing secretory IgA against SARS-CoV-2.
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