Can Moms Pass COVID-19 Immunity To Their Newborns?

Corona spread

New study, published Jan. 29 in the journal JAMA Pediatrics, scientists analyzed blood samples from more than 1,470 pregnant women, 83 of whom tested positive for antibodies for SARS-CoV-2, the coronavirus that causes COVID-19 at the time of delivery. Umbilical cord blood samples from the majority of babies born to these women also tested positive for antibodies, suggesting the babies picked up this passive immunity. 

The number of antibodies passed to the baby largely depended on the type and quantity of antibodies that were present in the mother, and when she caught COVID-19 during pregnancy.

“The longer [the] time between maternal infection and delivery, the greater the antibody transfer,” study authors Dr. Karen Puopolo and Dr. Scott Hensley of the University of Pennsylvania Perelman School of Medicine wrote in an email. This correlation held true whether the mother developed symptoms of COVID-19 or remained asymptomatic during her infection.

The transferred antibodies may provide protection to the newborn baby, but “work remains to be done to determine what levels and types of antibody are needed to protect newborns from SARS-CoV-2 infection, and how long those antibodies may last in the newborn circulation,” the authors said. Another big question is how well the transferred antibodies “neutralize” the coronavirus, meaning block its ability to infect cells, they said.

“It is hopeful to have this data,” said Dr. Flor Muñoz-Rivas, an associate professor of pediatric infectious disease at the Baylor College of Medicine in Houston, who was not involved in the study. By studying antibody transfer after natural COVID-19 infection, we can gather hints about whether vaccines given to pregnant people provide similar protection to new born Baby.

In the new study, the team specifically tested for antibodies that latch onto the coronavirus spike protein, a structure that sticks off the virus’s surface; the antibodies team looked for all target the “receptor-binding domain” (RBD), the part of the spike that binds directly to the receptor, or doorway, into cells. RBD antibodies are the most critical for neutralizing the coronavirus, Live Science previously reported. 

“But not all RBD antibodies can cross the placenta”, Muñoz-Rivas said. That’s because the placenta allows only certain antibodies through, using a special receptor and protein that transports antibodies into the organ. Only small, Y-shaped antibodies called immunoglobulin G (IgG) can fit into the receptor, so they alone can reach the fetus and provide immune protection, she said. 

Not all the babies got protection: 72 of the 83 babies born to antibody-positive mothers had IgG in their cord blood, and the overall quantity correlated with the IgG concentrations in their mothers’ blood.

Six of the babies’ mothers had relatively low IgG levels, suggesting that they were likely “so early in their infection that there had not been time for them to produce and transfer antibody across the placenta,” the authors said. Either that, or the mothers simply produced fewer antibodies than average, but this is a less likely scenario, they added. The other five babies’ mothers only tested positive for so-called IgM antibodies, which cannot cross the placenta. 

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