Infants Born to Mothers with COVID-19 Have Detectable Levels of Antibodies

BACKGROUND AND PURPOSE:

Zeng et al. (JAMA, 2020) examined antibody levels in 6 women with confirmed COVID-19, as well as their infants

Retrospective study
Setting
- Zhongnan Hospital of Wuhan University
Participants
- 6 hospitalized pregnant women with confirmed COVID-19
- Testing: Quantitative RT-PCR for SARS-CoV-2
- Patients delivered February 16 to March 6, 2020
Study design
- Maternal samples: Blood collected at delivery
- Neonatal samples
  - Blood and throat swabs at birth
- Cytokines and antibodies (IgG and IgM) also tested
- Performance characteristics of antibody test kits: IgM: 88.2% (sensitivity) and 99.0% (specificity) | IgG: 97.8% (sensitivity) and 97.9% (specificity)

6 mothers tested | All had mild clinical manifestations
- All delivered via cesarean in the third trimester in negative pressure isolation rooms
- Infants were isolated from their mothers immediately after delivery
Infant characteristics
- All had normal Apgar scores: 1-minute Apgar scores of 8 to 9 | 5-minute Apgar scores of 9 to 10
- All RT-PCR tests were negative for SARS-CoV-2

Antibody Testing

All infants had antibodies detected in their serum
Both IgG and IgM: 2 infants had both IgG and IgM concentrations higher than the reference rage (<10 AU/mL)
- Infant 1: IgG level = 125.5; IgM level = 39.6 AU/mL
- Infant 2: IgG level = 113.91; IgM level = 16.25 AU/mL
- All mothers also had elevated levels of IgG and IgM
IgG only: 3 infants had elevated IgG levels
- Infant 1: 75.49 AU/mL
- Infant 2: 73.19 AU/mL
- Infant 3: 51.38 AU/mL)
- All mothers had elevated IgG and 2 also had elevated IgM levels
Inflammatory cytokine IL-6 was significantly increased in all infants
Infants asymptomatic (as of March 8, 2020)

None of the infants born to mothers with COVID-19 had SARS-CoV-2 detected in their serum or throat swab by RT-PCR
- However, virus-specific antibodies were found
2 infants had elevated IgM concentrations
- “Unexpected” finding as IgG crosses placenta, but, due to size, IgM does not
- The authors hypothesize that this finding could be due to placenta damage or the infant producing antibodies
- Infant responding to in-utero infection with antibody production would suggest vertical transmission of SARS-CoV-2
Some limitations include
- Small sample size
- Lack of cord blood, amniotic fluid, and breast milk samples
- Incomplete information on the outcome of the infants

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