• Infants born to mothers vaccinated against COVID-19 may have protection conferred via transplacental transfer of antibodies
• Halasa et al. (NEJM, 2022) assessed the effectiveness of maternal vaccination during pregnancy against hospitalization for Covid-19 among infants <6 months

• Case–control test-negative study
• Participants
  • Infants <6 months who were hospitalized between July 2021 and March 2022 across 22 U.S. states
    • Cases: Hospitalized for COVID-19
    • Controls: Hospitalized without COVID-19
• Exposures
  • Maternal COVID-19 vaccination
• Study design
  • Full maternal vaccination was defined as two doses of mRNA vaccine
  • The primary variants in circulation were
    • Delta: July 2021 to December 2021
    • Omicron: December 2021 to March 2022
• Primary outcome
  • Vaccine effectiveness in infants

• Case infants: 537 | Control infants: 512
  • Cases: Hospital admission occurred during
    • Delta: 181 infants
    • Omicron: 356 infants
  • Median infant age: 2 months
• Maternal vaccination among cases and controls
  • Cases: 16% born to vaccinated mothers
  • Controls: 29% born to vaccinated mothers
• Case infant outcomes
  • Received intensive care: 21%
    • Received mechanical ventilation or vasoactive infusions: 12%
  • Deaths: 2 cases (neither mother was vaccinated)
• Effectiveness of maternal vaccination against infant hospitalization for COVID-19
  • Overall: 52% (95% CI, 33 to 65)
  • During Delta: 80% (95% CI, 60 to 90)
  • During Omicron: 38% (95% CI, 8 to 58)
• Effectiveness by vaccination timing
  • Vaccination >20 weeks: 69% (95% CI, 50 to 80)
  • Vaccination <20 weeks: 38% (95% CI, 3 to 60)

• Maternal vaccination against COVID-19 was associated with a reduced risk of infant (<6 months of age) hospitalization due to COVID-19
• The authors state

In this real-world evaluation, maternal vaccination with mRNA vaccines was associated with a substantial reduction in the risk of Covid-19–related hospitalization and critical illness among young infants, although reductions were less pronounced when the omicron variant was predominant

These findings provide additional support for the current recommendations regarding Covid-19 vaccination during pregnancy

Maternal Vaccination and Risk of Hospitalization for Covid-19 among Infants

Related ObG Topics: