The FDA has updated the label for Sanofi’s Flublox influenza vaccine to include safety data from a study of over 48,000 pregnant individuals.

RT’s Three Key Takeaways:

  1. FDA Label Update: The FDA has updated Sanofi’s Flublox influenza vaccine label to include new safety data for use in pregnant individuals.
  2. Large-Scale Study: A study involving over 48,000 pregnant individuals found that Flublox demonstrated no increased risk of adverse pregnancy, birth, or neonatal outcomes compared to a standard-dose flu vaccine.
  3. Supports Vaccination Guidance: The findings support current recommendations from health authorities for flu vaccination during pregnancy to reduce the risk of severe illness and complications from influenza.

The US Food and Drug Administration (FDA) has updated the label for Sanofi’s Flublox influenza vaccine to include data from a new safety study involving pregnant individuals 18 years and older.

The results from the study of more than 48,000 pregnant individuals across multiple flu seasons were recently published in American Journal of Obstetricians and Gynecologists Global Reports and demonstrate Flublox safety is consistent with a standard-dose flu vaccine and pregnancy-related outcomes in the general population.

“Today, we’re proud to announce an important update to our label for Flublox, from one of Sanofi’s largest flu vaccine safety studies ever done in pregnant individuals, an important at-risk population group for influenza. Here at Sanofi, we strive to bring immunizations to populations at various stages of life,” says Thomas Grenier, head of vaccines, North America, Sanofi, in a release.

This study was a post-licensure, observational, retrospective safety surveillance study of 48,781 pregnant individuals, including those with chronic conditions. In the study, patients were immunized with either Flublok quadrivalent (30.7%; n=14,981) or with a comparator standard-dose quadrivalent inactivated influenza vaccine (67.3%; n=33,800) during the Northern Hemisphere influenza seasons 2018-2019 and 2019-2020.

Immunization occurred within 28 days prior to pregnancy or during pregnancy. The efficacy of Flublox (quadrivalent) is relevant to Flublox (trivalent) because both vaccines are manufactured using the same process and have overlapping compositions.

Results showed:

  • Flublox demonstrated no increased risk of pregnancy, birth, or neonatal/infant outcomes when compared to a standard-dose flu vaccine and estimated pregnancy outcomes for the general population.
  • The most frequently reported pregnancy outcomes in the Flublox Quadrivalent and SD-IIV4 groups respectively were eclampsia/preeclampsia (8.4% in both cohorts), preterm labor (3.6% and 3.5%), spontaneous abortion (3.1% and 3.0%), congenital/fetal anomalies detected during pregnancy (2.4% in both cohorts), placental abruption (0.8% and 0.7%) and stillbirth/fetal death (0.4% and 0.5%).
  • The most frequently reported birth and neonatal/infant outcomes in the Flublox Quadrivalent and SD-IIV4 groups were small for gestational age (SGA) (8.8% and 8.7%), major congenital anomalies (7.7% in both cohorts), preterm birth (7.3% and 7.5%), low birth weight (LBW) (5.9% and 5.8%) and failure to thrive (1.0% and 1.1%), respectively.1

Per the Centers for Disease Control and Prevention, pregnant and postpartum (up to two weeks after the end of pregnancy) individuals are at higher risk for severe illness and complications from flu, particularly during the second and third trimesters. The American College of Obstetricians and Gynecologists recommends full vaccination during pregnancy, as this is when the risk of severe illness is highest.

The CDC, Advisory Committee on Immunization Practices, and the American College of Obstetricians and Gynecologists recommend that individuals who are or will become pregnant during flu season receive an inactivated or recombinant vaccine as soon as it is available, as pregnant persons with influenza may be at increased risk for adverse pregnancy outcomes, including preterm labor and delivery.

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