Assessment of timing of transplacental antibody transfer after
SARS-CoV-2 vaccination against the Omicron variant: A prospective cohort
study
Abstract
Objective To determine the optimal timing of SARS-CoV-2
vaccination during pregnancy by investigating the transplacental
transfer of SARS-CoV-2 antibodies from maternal SARS-CoV-2 vaccination
or infection. Design Prospective cohort study Setting
Samples were collected between June 6, 2022 and September 20, 2022 in
Taiwan. Sample Seventy-five maternal-cord pairs, including 38
pairs with a primary maternal SARS-CoV-2 infection by the Omicron
variant (BA.2.3.7) and 37 pairs without maternal infection.
Methods SARS-CoV-2 antibodies against the nucleocapsid
(anti-N), receptor-binding domain of the spike protein (anti-S), and the
neutralizing antibody (nAb) titers against different SARS-CoV-2 variants
were measured for the maternal-cord pairs. The participants were
categorized based on the timing of their last vaccination, including
during the third (T3) and second trimesters (T2) and before/during the
first trimester (T1). Comparison of anti-spike protein antibody and
neutralizing antibody concentrations was analyzed using the
Kruskal-Wallis test followed by a post-hoc Mann-Whitney U test.
Main Outcome Measures Anti-S concentrations of maternal and
cord serum among T1, T2, and T3 groups. Results Among
participants without SARS-CoV-2 infection, the highest anti-S levels (
p value for anti-S levels in maternal and cord plasma were
<0.001 and <0.001, respectively) and highest nAb
potency against both the Wuhan and Omicron strains ( p value for
nAb against Omicron strain were both <0.001 for maternal and
cord plasma) were observed in maternal and cord plasma in the T3 group.
Conclusions A booster vaccine dose during the third trimester
can provide maximum transplacental protection against the Wuhan
wild-type strain and Omicron variant. Pregnant women are encouraged to
receive vaccinations during pregnancy, ideally in the third trimester,
for the highest level of neonatal protection.