COVID Vax in Pregnancy Shields Babies From Hospitalization

Infants whose mothers were vaccinated against COVID-19 during pregnancy had significant protection against hospitalization for the disease, according to a CDC report.

Babies younger than 6 months old who were born to mothers who completed a two-dose mRNA vaccination series during pregnancy were 61% less likely to be hospitalized with COVID-19 (95% CI 31-78), reported Natasha B. Halasa, MD, of Vanderbilt University Medical Center in Nashville, Tennessee, and colleagues.

Vaccine effectiveness was highest when mothers were immunized later in pregnancy, they noted in the Morbidity and Mortality Weekly Report:

• First 20 weeks of pregnancy: 32% (95% CI -43 to 68)
• After 21 weeks’ gestation: 80% (95% CI 55-91)

“The bottom line is that maternal vaccination is a really important way to help protect these young infants,” said Dana Meaney-Delman, MD, MPH, chief of the CDC’s Infant Outcomes Monitoring Research and Prevention Branch, during a press call. While previous research has shown that COVID-19 antibodies can cross the placenta, this study provides real-world evidence that they can protect babies against severe illness, she added.

Meaney-Delman underscored the risk of severe COVID-19 illness during pregnancy, stating that it is important for pregnant people to get vaccinated at any point in pregnancy to protect themselves. The CDC recommends that people who are pregnant, breastfeeding, or planning to get pregnant get vaccinated and stay up-to-date on their COVID-19 immunizations.

In this study, Halasa’s group assessed maternal vaccine effectiveness against hospitalization for their newborn infants, comparing maternal characteristics among infants hospitalized for COVID and those hospitalized for other reasons. The researchers analyzed data on infant hospitalizations from July 2021 to January 2022 from Overcoming COVID-19, a case-control study of 20 pediatric hospitals in 17 states.

Mothers who were considered to be vaccinated received either the Pfizer/BioNTech or Moderna two-dose vaccination series up to 2 weeks before delivery. Those who were partially vaccinated, vaccinated after pregnancy, received the Johnson & Johnson vaccine, or were immunized in the 2 weeks leading up to delivery were excluded from the analysis. The researchers adjusted their models for infant age and sex, U.S. Census region, calendar time of admission, and race and ethnicity.

They included 379 hospitalized infants in the study, 176 of whom were hospitalized for COVID and 203 who were hospitalized for other causes. The median age of infants was 2 months, 21% had at least one underlying medical condition, and 22% were born prematurely.

Among the 176 infants who were hospitalized with COVID-19, 84% were born to mothers who were not vaccinated; 43 were admitted to the ICU, and 25 developed critical illness and received life support. One infant received extracorporeal membrane oxygenation, and one died (the mothers in both of these cases were not vaccinated).

Those in the hospitalization group had similar rates of underlying medical conditions and prematurity to those in the control group, but were more likely to be Black or Hispanic.

Halasa and colleagues acknowledged that vaccine effectiveness could not be assessed directly against specific variants in this study, and the sample size was too small to assess vaccine effectiveness based on the trimester it was administered.

This research was also limited by the fact that it could not assess maternal infection with SARS-CoV-2, and it was subject to residual confounding from behavioral differences in the case and control groups. While booster shots are recommended during pregnancy, the researchers were unable to assess vaccine effectiveness of additional doses because of the study’s small sample size.