Effectiveness of Maternal Influenza Vaccination during Pregnancy against Medically Attended Influenza among Infants <6 Months of Age, New Vaccine Surveillance Network (NVSN), 2016-2017 through 2024-2025 Influenza Seasons
- Presentation Day/Time: Tuesday, April 21, 9:35 AM
- Presenter: Savanah Russ, PhD, MPH, National Center for Immunization and Respiratory Diseases, Influenza Division
The Issue
- Infants less than six months old are at high risk for severe influenza illness, but there is no licensed influenza vaccine available for this age group. Maternal influenza vaccination during pregnancy is effective at preventing influenza illness among these infants, but the level of protection can vary by vaccination timing during pregnancy and infant age at the time of their illness.
What We Did
- We estimated maternal influenza vaccine effectiveness (VE) against influenza illness among infants less than six months old by timing of maternal influenza vaccination and infant age. A total of 410 case infants and 7,101 control infants were included; of which 47% and 53% were born to mothers vaccinated during pregnancy, respectively.
What We Found
- We found that VE was significant for infants born to mothers who were vaccinated at 20 weeks or later in their pregnancies, with 48% VE among infants who were 0–2 months old at the time of their illness and 33% VE among infants who were 3–5 months old at the time of their illness. VE was not significant for infants born to mothers who were vaccinated before reaching 20 weeks in their pregnancies.
What This Means
- These findings support current recommendations for influenza vaccination during pregnancy as well as consideration of maternal vaccination for women in their third trimester, as soon as influenza vaccines are released each season, to optimize protection for their infants.
