Pregnant women who contract Covid-19 pass protective antibodies to their newborns, a finding that could help determine when the women should get Covid vaccines.
The study found that of 83 women who tested positive for Covid, 72 passed on IgG antibodies to the newborn in levels consistent with the mother’s antibodies. The levels seemed unaffected by whether the mother had a mild, moderate, severe or asymptomatic form of the virus, but did increase the earlier in her pregnancy the mother had become infected.
“This transfer appears to be pretty efficient,” said study co-senior author Karen Puopolo, MD, PhD, a neonatologist at Children’s Hospital of Philadelphia, an associate professor of Pediatrics at the University of Pennsylvania Perelman School of Medicine and Chief of the Section on Newborn Medicine at Pennsylvania Hospital. “In some of the cases, the newborn’s blood concentration of SARS-CoV-2 antibodies was even higher than the mother’s.”
Equally reassuring, none of the infants had IgM antibodies, which suggests that while mothers can pass along antibody protection, transmitting the actual virus through the placenta would seem to be very rare, as expected.
Vaccinations early in pregnancy may be better
In addition to indicating that vaccinating pregnant women would benefit their babies, the study could also help determine when that vaccination should happen.
In the study, all the women who were infected at least 17 days before delivery passed the protective antibodies to their infants.
The authors also noted that the transfer of Covid antibodies from mother to child seems to match how mothers pass on antibodies from other vaccines.
“Our findings are aligned with studies of vaccine-elicited antibodies to pertussis, rubella, hepatitis B, and influenza,” they wrote. “When (Covid) vaccines are widely available, the optimal timing of maternal vaccination during pregnancy will need to consider maternal and fetal factors including the time needed to ensure neonatal protection.”
Early second trimester could be optimal
A JAMA editorial that appeared with the study said that accounting for the two-shot timing of the Covid vaccine and how long it takes to pass along antibodies, “maternal vaccination starting in the early second trimester of gestation might be optimal to achieve the highest levels of antibodies in the newborn.”
However, further study is needed to determine how effective that protection is for the baby and how long it lasts. It notes that the benefit of other maternal vaccines begins to fade rapidly by the time the child is two-months-old. It also raised several other considerations that remain unanswered.
“To what extent can antibodies transferred through breast milk protect lactating newborns? Should infants be vaccinated regardless of maternal infection, and if so, what is the best timing to initiate infant vaccines? Is there a potential detrimental effect of maternal antibodies on infant responses to active immunization? And what would be the optimal vaccine and vaccination regimen for infants, considering their risk and unique immunologic needs?” they ask. “While maternal immunization is likely the best available option to protect both pregnant and lactating mothers as well as their infants during the COVID-19 pandemic, the importance of collecting data to answer these outstanding questions cannot be overemphasized.”