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.