Table 2.

Summary of various studies evaluating vaccination during lactation and human milk antibodies with regards to the mRNA-1273 and BNT162b2 vaccines including sample size of lactating women, timepoints measured, and mean infant age.

Author	Vaccines	Measured antibodies (Ab) in human milk	Sample size (lactating women)	Timepoints	Mean infant age	Findings overall	Findings on milk IgG	Findings on milk IgA
Kelly et al. (102)	BNT162b2	Anti-spike IgG and IgA Ab levels	5	1. Pre-vaccine 2. 10-19 days post vaccination 3. 20-29 days post vaccination 4. 30-39 days post vaccination 5. >40 days post vaccination	9.8 months	-Both IgG and IgA levels were increased post vaccination	-Anti-spike IgG remained significantly increased 20 days post dose 1 to >40 days compared to pre-vaccine levels	-Anti-spike specific IgA were significantly increased 2 weeks post dose 1 to >40 days compared to pre-vaccine levels, although a decreasing level of mean IgA was observed at >40 days post dose 1
Perl et al. (103)	BNT162b2	Anti-spike IgG and IgA Ab levels	84	Pre-vaccine and weekly samples up to 6 weeks after first dose.	10.32 months	-Both IgG and IgA levels remained elevated in human milk 6 weeks post vaccination	-Mean anti-COVID specific IgG levels were low until week 3, and dramatically increased at week 4 and remained elevated at weeks 5 and 6	-Mean anti-COVID specific IgA levels increased significantly at 2 weeks post-first dose, decreased before the 2nd dose, and increased sharply 1 week post-second dose at week 4. -IgA levels remained elevated throughout the rest of the time points although steadily decreased.
Rosenberg-Friedman et al. (104)	BNT162b2	Anti-spike and RBD IgG and IgA Ab levels compared with a pre-pandemic control population	10 healthcare workers	1. 7 days post-first dose 2. 14 days post-first dose 3. 7 days post-second dose 4. 14 days post-second dose	5.13 months	-IgG: IgA ratios were calculated and suggested that IgA was the greatest at all time points, although the ratio increased significantly at 7 and 14 days post second dose, suggesting an increase in IgG over time post second dose. IgG and IgA levels increased at each time point and stopped increasing on 14 days post-second dose. - IgA production rate decreased 14 days post-second dose. IgG peaked at 14 days post-second dose whereas IgA showed a small decline at 14 days post-second dose.	-Anti-spike IgG at 7 days after first dose did not increase significantly compared to the controls, although increased significantly on day 14. Levels peaked on 7 days post second dose. -Anti-RBD IgG had a similar trend as above	-Anti-spike IgA increase significantly compared to controls 14 days after first dose. Levels peaked 7 days after second dose. -Anti-RBD IgA had a significant increase 7 days post second dose compared to controls.
Gray et al. (96)	mRNA-1273 and BNT162b2	Anti-spike and RBD IgG, IgA, and IgM Ab levels	31	1. Before first dose 2. After 1st dose: day of and before the 2nd dose 3. 2-6 weeks post-second dose	7.3 months (median)	-A significant increase of COVID specific IgG, IgA, and IgM was measured after first and after second dose compared to baseline.	-Increase in IgG was measured after second dose suggesting the boost facilitated an increase in transfer of IgG to human milk.	-IgA transfer in human milk did not increase after second dose compared to IgA levels after first dose.
Young et al. (105)	mRNA-1273 and BNT162b2	Anti-RBD IgG and IgA Ab levels	30	1. pre-vaccine 2. 18 days post-first dose 3. 18 days post-second dose 4. 90 days post-second dose	7.5 months	-Both IgG and IgA levels were increased post vaccination	-Large increase in IgG 18 days post-first dose and an additional increase 18 days after the second dose. It was followed by a decline at 90 days post-second dose.	-IgA levels increased at 18 days post-first dose, and didn’t further increase post-second dose
Golan et al. (25)	mRNA-1273 and BNT162b2	Anti-RBD IgG and IgA Ab levels in human milk and IgG and IgM in serum	50	1. Pre-vaccine 2. After first dose: day of and before the second dose 3. 4-10 weeks after the second dose	4.7 months (median)	-Both IgG and IgA levels were increased post vaccination -IgG levels were positively correlated between blood and milk between 4-10 weeks after the second dose	-IgG levels increased after the first dose and had a greater increase after the second dose.	- IgA levels significantly increase after the first dose, with no further increase 4-10 weeks after second dose.
Lechosa-Muñiz et al. (79)	BNT162b2, mRNA-1273 and ChAdOx1-S	Anti-RBD IgG and IgA Ab levels in human milk and serum	110	30 days after the second dose of the vaccine (or after first dose for ChAdOx1-S)	15.9 months	Significantly higher levels of IgG and IgA were found after mRNA-based vaccine vs. ChAdOx1-S.
Selma-Royo et al. (80)	BNT162b2, mRNA-1273 and ChAdOx1	Anti-RBD IgG and IgA Ab levels in human milk	86	pre-vaccination, 1 week, 2 weeks, and 3–4 weeks post the 1st dose of vaccine; 1 week, 2 weeks, and 3–4 weeks post 2nd dose.	11-14.3 months	-Significant increase in IgA and IgG in milk with higher levels after second dose. -Antibody levels depend on vaccine type.	-IgG levels increased after the first dose with greater increase after the second dose.	- IgA levels after vaccination were lower compared to milk from COVID-19-infected women.