A pair of new US studies detail COVID-19 risk and protective factors in infants in the first 6 months of life, one showing that being born during the pandemic is linked to impaired neurodevelopment, and the other finding that breast milk may contain SARS-CoV-2 antibodies that are not significantly reduced by pasteurization for as long as 6 months.
Maternal COVID not linked to impaired development
A study today in JAMA Pediatrics led by Columbia University researchers involved 255 infants born to COVID-19–infected and uninfected women between March and December 2020. They assessed infant neurodevelopment using the third edition of the Ages & Stages Questionnaire (ASQ-3) at 6 months and conducted a secondary analysis of 62 infants born at the same medical center from November 2017 through January 2020.
Among the 255 infants, 114 (44.7%) had been exposed to COVID-19 in utero, and 141 (55.3%) were unexposed. Median maternal age at delivery was 32.0 years. Most mothers had asymptomatic (34%) or mild (62%) illness and were infected in the second (47%) or third (31%) trimester. Four percent of mothers were severely ill, and 22% were infected in the first trimester.
Regardless of COVID-19 status or timing, in utero exposure to maternal COVID-19 infection was not tied to significant differences in any of the five ASQ-3 subdomains. But relative to infants born before the pandemic, those delivered after January 2020 scored significantly lower on the gross motor (average difference, -5.63), fine motor (−6.61), and personal-social (−3.71) areas after adjustment.
The researchers said that the lack of neurodevelopmental differences between infants with and without COVID-19 exposure in the womb and the differences between infants born before and after the emergence of COVID-19 suggests that pandemic-related stresses such as job loss and food and housing insecurity could have contributed to the impairments.
"Consistent with our finding that infants born to women who were in the first trimester of pregnancy during the pandemic peak had the lowest scores in gross motor, fine motor, and personal-social subdomains, data from numerous cohort studies have demonstrated that prenatal perceived stress, loneliness, and objective stress, especially during early gestation, are associated with an increased risk for adverse neurodevelopment in children," the researchers wrote.
They called for long-term monitoring of children born during the pandemic and for further investigation into the role of maternal stress in impaired infant neurodevelopment.
Antibodies could protect infants for up to 6 months
In a study yesterday in Pediatrics, a team led by Children's Hospital Los Angeles researchers used an enzyme-linked immunosorbent assay (ELISA) to measure SARS-CoV-2 antibodies and neutralization capacity in 30 pregnant or breastfeeding women from December 2020 to August 2021. Antibody concentrations were assessed prevaccination and at 1, 3, and 6 months after vaccination as well as after pasteurization of the milk.
While previous research has suggested that maternal mRNA COVID-19 vaccination leads to the presence of SARS-CoV-2 antibodies in breast milk for as long as 6 weeks, the duration of antibody neutralization and persistence after pasteurization were unclear, the authors said.
All breast milk samples collected at 1 month (24 of 24) and most collected at 3 months (25/27) and 6 months (9/12) were above the cutoff value for SARS-CoV-2 immunoglobulin G (IgG) antibodies.
IgG levels peaked 1 month after vaccination and remained above prevaccination levels for 6 months or more. Immunoglobulin A (IgA) antibodies were detected 1 and 3 months after vaccination but had waned by 6 months, relative to baseline.
IgG and IgA in the breast milk correlated with serum IgG at the same point in time, and SARS-CoV-2 neutralization was observed in 83.3% of milk samples at 1 month after vaccination, 70.4% at 3 months, and 25.0% at 6 months.
"Although IgG levels decreased from the 1-month postvaccination peak, SARS-CoV-2–specific IgG persisted above prevaccination levels at the half-year mark, and 75% of milk tested remained positive at 6 months," the researchers wrote.
Neutralization was most strongly associated with IgG. Both before and after pasteurization, milk samples had similar IgG levels and neutralization (57.7% vs 58.7% inhibition), but immunoglobulin M (IgM) and IgA concentrations were reduced after pasteurization.
While cautioning that the correlate of protection against SARS-CoV-2 is unknown, the authors said the findings are encouraging. "This [sic] data reinforces evidence for breastfeeding recommendations in mothers after vaccination and helps inform milk bank policies concerning donations from vaccinated women, because milk-delivered antibodies could offer human milk-fed children protection against SARS-CoV-2 infection," they wrote.