Effectiveness of Maternal Vaccination with mRNA COVID-19 Vaccine during Pregnancy against COVID-19–Associated Hospitalization in Infants Aged <6 Months.

CDC’s Morbidity and Mortality Weekly Report (MMWR):

During July 2021–January 2022, maternal completion of a 2-dose primary mRNA COVID-19 vaccination series during pregnancy was associated with reduced risk for COVID-19 hospitalization among infants aged <6 months in a real-world evaluation at 20 U.S. pediatric hospitals during a period of Delta and Omicron variant circulation.

COVID-19 during pregnancy is associated with severe illness and death, and pregnant women with COVID-19 are more likely to experience preterm birth, stillbirth, and other pregnancy complications. Vaccination is recommended for pregnant women to prevent COVID-19, including severe illness and death.

Infants are also at risk for life-threatening complications from COVID-19, including acute respiratory failure. Evidence from other vaccine-preventable diseases suggests that maternal immunization can provide protection to infants, especially during the high-risk first 6 months of life, through passive transplacental antibody transfer.

Recent studies of COVID-19 vaccination during pregnancy suggest the possibility of transplacental transfer of SARS-CoV-2–specific antibodies that might provide protection to infants. COVID-19 vaccination during pregnancy is associated with detectable maternal antibodies in maternal sera at delivery, breast milk, and infant sera indicating transfer of maternal antibodies.

Key Points Summary

What is already known about this topic?

COVID-19 vaccination during pregnancy is recommended to prevent severe illness and death in pregnant women. Infants are at risk for COVID-19–associated complications, including respiratory failure and other life-threatening complications.

What is added by this report?

Effectiveness of maternal completion of a 2-dose primary mRNA COVID-19 vaccination series during pregnancy against COVID-19 hospitalization among infants aged <6 months was 61%. Effectiveness of completion of the primary COVID-19 vaccine series early and later in pregnancy was 32% and 80%, respectively.

What are the implications for public health practice?

Completion of a 2-dose mRNA COVID-19 vaccination series during pregnancy might help prevent COVID-19 hospitalization among infants aged <6 months.

Conclusions

Completion of a 2-dose primary mRNA COVID-19 vaccination series during pregnancy was associated with reduced risk for COVID-19–associated hospitalization among infants aged <6 months, and protection was higher among infants whose mothers were vaccinated later in pregnancy. Additional evaluation should examine timing of vaccination before pregnancy compared with during pregnancy.

CDC recommends that women who are pregnant, are breastfeeding, are trying to get pregnant now, or might become pregnant in the future get vaccinated and stay up to date with COVID-19 vaccination.