Characteristics of studies with anti-SARS-CoV-2 antibodies detected in breastmilk
| Author | Maternal characteristics | Time interval between maternal symptoms onset and Ig positive | Assay and immunoglobulin characteristics | Infant characteristics | Comments |
| Dong et al 28 | # mothers BM Ig positive: 1. # BM samples tested: 6. # positive samples: 6. | 26 days | Assay method: ELISA. Antigen used: S-protein. Type of Ig: IgA and IgG. | Type of feeding: NK. Symptoms: no. Infant RT-PCR positive: no. | BM IgG remained positive for 58 days after symptom onset. Maternal serum IgG positive at 26 days and remained positive 58 days after symptom onset. Infant serum IgG positive at DoL 25 but negative at DoL 44. |
| Fenizia et al 20 | # mothers BM Ig positive: 1. # BM samples tested: 1. # positive samples: 1. | NK | Assay method: chemiluminescence immunoassay. Antigen used: nucleocapsid and S-protein. Type of Ig: IgG and IgM. | Type of feeding: NK. Symptoms: NK. Infant RT-PCR positive: no. | BM positive for both virus RNA and antibodies. |
| Gao et al 29 | # mothers BM Ig positive: 2. # BM samples tested: 2. # positive samples: 2. | 17–22 days | Assay method: chemiluminescence immunoassay. Antigen used: NK. Type of Ig: IgG and IgM. | Type of feeding: BMS1 and EBM.1
Symptoms: NK. Infant RT-PCR positive: no. | Both infants had positive serum IgG, one also had positive serum IgM. (Third mother with positive IgM in BM not included, had negative RT-PCR in throat swab but positive serum IgM.) |
| Luo et al 30 | # mothers BM Ig positive: 4. # BM samples tested: 4. # positive samples: 4. | 13–45 days | Assay method: ELISA. Antigen used: NK. Type of Ig: IgM. | Type of feeding: BMS. Symptoms: no. Infant RT-PCR positive: no. | BM RT-PCR negative All four mothers had serum IgG and IgM positive after delivery. All four mothers had negative PCR at time of BM sampling. |
| Pace et al 31 | # mothers BM Ig positive: 18. # BM samples tested: 37. # positive samples: 37. | 0–20 days (three asymptomatic) | Assay method: ELISA. Antigen used: spike (S2 and RBD) and nucleocapsid. Type of Ig: IgA and IgG. | Type of feeding: BF5 and MF.13
Symptoms: NK. Infant RT-PCR positive: yes.2 | BM RT-PCR negative, one breast swab RT-PCR positive. Serum Ig not tested. All mothers had positive PCR before first BM sample, two had negative PCR before second sample and one had negative PCR before third sample. |
| Peng et al 32 | # mothers BM Ig positive: 8. # BM samples tested: 27. # positive samples: 21. | 3–79 days | Assay method: ELISA. Antigen used: NK. Type of Ig: IgM. | Type of feeding: NK.* Symptoms: NK. Infant RT-PCR: NK. | BM RT-PCR negative. Serum Ig not tested. Three mothers had IgM negative at 47–72 days. IgM positive samples collected at 31±19 days and IgM negative samples at 43±21 days after symptom onset.† |
| Preβler et al 14 | # mothers BM Ig positive: 1. # BM samples tested: NK. # positive samples: 1. | NK | Assay method: NK. Antigen used: nucleocapsid. Type of Ig: IgG. | Type of feeding: NK. Symptoms: yes. Infant RT-PCR: no. | Maternal serum IgG positive 4–5 weeks after symptom onset. Infant RT-PCR and serum antibodies. negative. |
| Van Keulen et al 15 | # mothers BM Ig positive: 24. # BM samples tested: 24. # positive samples: 24. | Mean 5.9 (SD 2.6 weeks) | Assay method: ELISA and bridging ELISA. Antigen used: S-protein, RBD and N protein. Type of Ig: IgA (S-protein) and total Ig (RBD and N protein). | Type of feeding: NK. Symptoms: NK. Infant RT-PCR: NK. | BM RT-PCR not tested. IgA present for at least 13 weeks from symptom onset. |
| Walczak et al 33 | # mothers BM Ig positive: 1. # BM samples tested: NK. # positive samples: NK. | NK | Assay method: microsphere immunoassay. Antigen used: NK. Type of Ig: IgA, IgG and IgM. | Type of feeding: NK. Symptoms: NK. Infant RT-PCR: no. | Author states immunoassay not validated, parent serum immunoglobulin IgG and IgM positive. |
| Yu et al 34 | # mothers BM Ig positive: 1. # BM samples tested: 2. # positive samples: 2 (for IgG, negative for IgM). | 10 days | Assay method: NK. Antigen used: NK. Type of Ig: IgG and IgM. | Type of feeding: BF. Symptoms: yes. Infant RT-PCR positive: yes. If yes: for how long: 13 days. | BM RT-PCR negative. Repeat BM IgG remained positive on day 26 postsymptom onset. Maternal serum IgG positive on days 15 and 19. Infant serum IgG and IgM positive on day 13. |
*Unable to distinguish feeding practices of those who tested Ig positive and Ig negative.
†No statistical difference found (Mann-Whitney U test, p=0.052).
#, number of; BF, breast feeding; BM, breastmilk; BMS, breastmilk substitute; DoL, day of life; Ig, immunoglobulin; NK, not known; RT-PCR, real time polymerase chain reactionPCR; S-protein, spike protein.