Vertical transmission and humoral immune response following maternal
infection with SARS-CoV-2 - A prospective multicenter cohort study
Abstract
Objective: To explore maternal humoral immune responses to severe acute
respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and the rate
of vertical transmission. Design: A prospective cohort study. Setting:
Two university-affiliated medical centers in Israel. Population: Women
positive for SARS-CoV-2 reverse-transcription-polymerase-chain-reaction
(RT-PCR) test, during pregnancy were enrolled just prior to delivery.
Methods: Levels of anti-SARS-CoV-2 spike-IgM, spike-IgG and
nucleocapsid-IgG were tested in maternal and cord blood at delivery, and
neonatal nasopharyngeal swabs were subjected to PCR testing. Main
outcomes measures: The primary endpoint was the rate of vertical
transmission, defined as either positive neonatal IgM, positive neonatal
IgG with sero-negative mother or positive neonatal PCR. Results: Among
72 women, 36 (50%), 39 (54%) and 30 (42%) were positive for
anti-spike-IgM, anti-spike-IgG and anti-nucleocapsid-IgG, respectively
(p<0.0001 for IgG antibodies-comparison). At least 8/72 (11%)
neonates were infected in utero; one had a positive PCR result and seven
had positive IgG antibodies while their mothers were seronegative for
the same IgG. IgM was not detected in cord blood. Anti-nucleocapsid-IgG
and anti-spike-IgG were detected in 83% and 85% of neonates of
seropositive mothers, respectively (Pearson coefficient correlation 0.8,
p<0.001). The highest rate of positive maternal serology tests
was 8-12 weeks post-infection (89% anti-spike IgG, 78% anti-spike-IgM
and 67% anti-nucleocapsid-IgG). Thereafter, the rate of positive
serology tests declined gradually; at 20 weeks post-infection, only
anti-spike-IgG was detected in 33-50%. Conclusions: The rate of
vertical transmission was at least 11%. Vaccination should be
considered 3 months post-infection in pregnant women due to a decline in
antibody levels.