Study suggests maternal COVID-19 vaccination protects babies

Baby snuggling on mom's shoulder
Baby snuggling on mom's shoulder

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COVID-19 vaccination during pregnancy—already known to protect women from hospitalization and severe complications—can also protect babies younger than 6 months, researchers reported today.

In other COVID-19 research developments, a separate team that looked at COVID-19 hospitalizations in kids found that levels jumped dramatically during the Omicron variant surge, especially in kids younger than 4, a group not eligible yet for vaccination.

Real-world evidence of baby benefits

The study on the impact of COVID-19 vaccination during pregnancy on the youngest infants examined hospitalization trends across 20 children's hospitals in 17 states from July 2021 through January 2022. The team published its findings today in an early online edition of Morbidity and Mortality Weekly Report (MMWR).

At a Centers for Disease Control and Prevention (CDC) briefing today, Dana Meaney-Delman, MD, MPH, who wasn't involved in the study and heads the CDC's Infant Outcomes Monitoring Research and Prevention Branch, said scientists already now that SARS-CoV-2 antibodies are found in umbilical cord blood and can cross the placenta. However, she said it wasn't known if the maternal antibodies provided any protection to babies.

"Now we have real-world evidence in babies younger than 6 months," she said.

The study authors found that babies born to pregnant women who had received two doses of an mRNA vaccine were 61% less likely than those born to unvaccinated moms to be hospitalized with a COVID-19 infection.

Of 176 babies hospitalized with COVID-19 over the study period, 84% were born to mothers who were unvaccinated during pregnancy. Of 43 infants who were admitted to the intensive care unit, 88% had mothers who were unvaccinated. Of the critically ill babies, one died—a child of an unvaccinated mother.

Effectiveness was lower if a woman was vaccinated in early pregnancy, during the first 20 weeks, with protection at 32% versus 80% in later pregnancy. But researchers warn that the confidence interval is wide and that the pattern should be interpreted with caution.

Senior author Manish Patel, MD, with the CDC's COVID-19 Emergency Response Team, said the numbers were too small to look at the impact of vaccination by trimester. And Delman said there aren't any changes in recommendations that relate to the timing of COVID-19 vaccination during pregnancy.

She said vaccination levels in pregnant women are increasing and are encouraging, but aren't where health experts need them to be.

Maternal vaccination has been found to help young infants against other infections such as flu and pertussis, and now extend to COVID-19. "This new study will undoubtedly be factoring into my counseling sessions," Meaney-Delman said.

Omicron hits youngest kids hardest

In a snapshot of COVID-19 hospitalizations in children and adolescents, another research team examined data from 14 states covering July 2021 to January 2022, a time that covered Delta circulation, then quickly transitioned to Omicron in December.

Their findings also appear in an early online edition of MMWR.

Once the Omicron variant became dominant, hospitalizations in children and adolescents reached levels that were four time higher than those of Delta's peak. The largest increase in hospitalizations was in children ages 0 to 4, who weren't eligible for vaccination.

During the study period, adolescents ages 12 to 17 were the only pediatric group approved for COVID-19 vaccination during the entire study period. When researchers compared their hospitalizations to that of unvaccinated peers, they found that levels were six times higher in the unvaccinated group.

"All persons who are eligible for vaccination should receive and stay up to date with COVID-19 vaccines to reduce the risk for severe disease for themselves and others with whom they come into contact, including children who are currently too young to be vaccinated," the group wrote.

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