SARS-CoV-2 specific antibody trajectories in mothers and infants over two months following maternal infection

Abstract

Infants exposed to caregivers infected with SARS-CoV-2 may have heightened infection risks relative to older children due to their more intensive care and feeding needs. However, there has been limited research on COVID-19 outcomes in exposed infants beyond the neonatal period. Between June 2020 - March 2021, we conducted interviews and collected capillary dried blood spots from 46 SARS-CoV-2 infected mothers and their infants (aged 1-36 months) for up to two months following maternal infection onset (COVID+ group, 87% breastfeeding). Comparative data were also collected from 26 breastfeeding mothers with no known SARS-CoV-2 infection or exposures (breastfeeding control group), and 11 mothers who tested SARS-CoV-2 negative after experiencing symptoms or close contact exposure (COVID- group, 73% breastfeeding). Dried blood spots were assayed for anti-SARS-CoV-2 S-RBD IgG and IgA positivity and anti-SARS-CoV-2 S1 + S2 IgG concentrations. Within the COVID+ group, the mean probability of seropositivity among infant samples was lower than that of corresponding maternal samples (0.54 and 0.87, respectively, for IgG; 0.33 and 0.85, respectively, for IgA), with likelihood of infant infection positively associated with the number of maternal symptoms and other household infections reported. COVID+ mothers reported a lower incidence of COVID-19 symptoms among their infants as compared to themselves and other household adults, and infants had similar PCR positivity rates as other household children. No samples returned by COVID- mothers or their infants tested antibody positive. Among the breastfeeding control group, 44% of mothers but none of their infants tested antibody positive in at least one sample. Results support previous research demonstrating minimal risks to infants following maternal COVID-19 infection, including for breastfeeding infants.

Keywords: COVID-19; IgA; IgG; breastfeeding; infancy; pediatric.

Figure 1

Individual maternal IgG and IgA S/CO trajectories (dashed, colored lines) over two months following maternal infection onset or enrollment, and loess smooth curves (solid, colored lines) fit for each enrollment group: COVID+ (n = 36, n_obs = 116); COVID- (n = 6, n_obs = 18); BF control group, (n = 20, n_obs = 50, excluding samples collected post-vaccination). S/CO=1.0 (solid black line), S/CO=2.0 (dashed black line). Y-axis is truncated at S/CO = 10; samples with S/CO between 10-20 not shown (IgG n_subj = 12, n_obs = 19; IgA n_subj = 6, n_obs = 4).

Figure 2

Individual infant IgG and IgA S/CO trajectories (dashed, colored lines) with group-level loess smoothes (solid, colored lines) over two months following maternal infection onset or enrollment, by maternal study group: COVID+ (n = 25, n_obs = 66); COVID- (n = 7, n_obs = 18); and BF control group, excluding samples collected post-maternal vaccination (n = 15, n_obs = 35), S/CO=1.0 (solid black line), S/CO=2.0 (dashed black line). Y-axis is truncated at S/CO = 10; samples with S/CO between 10-20 not shown (IgG n_subj = 3, n_obs = 11; IgA n_subj = 2, n_obs = 3).

Figure 3

Predicted mean probability (with 95% credible intervals) of IgG and IgA seropositivity across all samples collected from COVID+ mothers (n = 36, n_obs = 116) and their exposed infants (n = 25, n_obs = 66). IgG infant = 0.54 [0.33 – 0.74], IgG maternal = 0.87 [0.76 – 0.95]. IgA infant = 0.33 [0.17 – 0.52]; IgA maternal = 0.85 [0.72 – 0.93].

Figure 4

Mean estimated probabilities (95% credible intervals) of IgG and IgA seropositivity (S/CO ≥1) in samples collected from COVID+ mothers (n = 36, n_obs = 116) and their exposed infants (n = 25, n_obs = 66) in the two months following maternal infection onset.

Figure 5

Predicted IgG S1 and S2 concentration (with 95% credible intervals) in COVID+ mothers (n = 26, n_obs= 66) and exposed infants (n = 9, n_obs=17) over two months following maternal infection onset.