FDA updates FLUBLOK flu vaccine label to include pregnant adults

FDA updates FLUBLOK flu vaccine label to include pregnant adults | Image Credit: © wladimir1804 - © wladimir1804 - stock.adobe.com.

The FDA has updated the label for the influenza vaccine FLUBLOK (Recombinant flu vaccine; Sanofi) to include safety information for pregnant individuals aged 18 years or older, according to Sanofi.¹

This update was made to comply with recommendations about annual flu vaccine administration before the end of October by the Centers for Disease Control and Prevention (CDC). FLUBOK’s safety in pregnant women has been found consistent with a standard-dose flu vaccine in a recent study.

The post-licensure, observational, retrospective safety surveillance study included over 48,000 pregnant patients from multiple flu seasons and was published in the American Journal of Obstetrics and Gynecology Global Reports. Individuals with chronic conditions were also included in the analysis.

Participants received either FLUBLOK Quadrivalent or a comparator influenza vaccine during the 2018 to 2019 and 2019 to 2020 Northern Hemisphere influenza seasons, with immunization taking place within 28 days before pregnancy or during pregnancy.

Results indicated no increased risk of adverse pregnancy, birth, or neonatal outcomes among patients taking FLUBOK compared to those taking the comparator vaccine. Eclampsia and preeclampsia were the most common outcome from both vaccines, with a rate of 8.4% in both groups.

Additional outcomes included preterm labor in 3.6% of the FLUBOK group and 3.5% of the comparator group, spontaneous abortion in 3.1% and 3%, respectively, fetal anomalies detected during pregnancy in 2.4% of both groups, placental abruption in 0.8% and 0.7%, respectively, and stillbirth or fetal death in 0.4% and 0.5%, respectively.

For neonatal outcomes, small for gestational age was the most common, with rates of 8.8% and 8.7%, respectively. This was followed by major congenital anomalies at 7.7% in both groups, preterm birth at 7.4% and 7.5%, respectively, low birth weight at 5.9% and 5.8%, respectively, and failure to thrive at 1% and 1.1%, respectively.

Additional safety information for FLUBLOK includes avoiding administration in patients with severe allergic reactions to any component of the vaccine. Administration should also be avoided in environments where there is a risk of injury from fainting. The immune response may be weakened in patients with a compromised immune system.

Side effects of FLUBLOK among patients aged 18 to 64 years include pain at administration site, headache, tiredness, and muscle pain. In those aged 65 years and older, administration site pain, tiredness, and headache are the most common side effects.

The CDC has noted that the risks of severe illness and complications related to influenza are increased in pregnant and postpartum patients up to 2 weeks after birth. This has led the American College of Obstetricians and Gynecologists (ACOG) to recommend full vaccination during pregnancy when the risk of severe illness is highest.

Maternal influenza infection during pregnancy has also been linked to an increased risk of seizures in offspring.² A recent study reported an adjusted hazard ratio (aHR) of 1.09 for seizures among these offspring vs those of uninfected pregnancies. Additional aHRs included 1.11 for febrile convulsions and 1.04 for epilepsy.

An inactivated or recombinant influenza vaccine should be given to patients who are or will become pregnant during flu season as soon as possible, according to the CDC, ACOG, and Advisory Committee on Immunization Practices.¹ This may reduce the risk of adverse pregnancy outcomes associated with influenza such as preterm labor and delivery.

References

1. FLUBLOK® (Influenza Vaccine) US label updated with one of Sanofi's largest flu vaccine safety studies in pregnant individuals. Sanofi. October 16, 2024. Accessed October 17, 2024. https://www.news.sanofi.us/2024-10-16-FLUBLOK-R-Influenza-Vaccine-US-label-updated-with-one-of-Sanofis-largest-flu-vaccine-safety-studies-in-pregnant-individuals
2. Krewson C. Maternal influenza linked to offspring seizure risk. Contemporary OB/GYN. September 23, 2024. Accessed October 19, 2024. https://www.contemporaryobgyn.net/view/maternal-influenza-linked-to-offspring-seizure-risk