What inactivated influenza vaccine is safe for use in pregnant women at any stage of pregnancy?

Safe Influenza Vaccine in Pregnancy

The inactivated influenza vaccine (either trivalent or quadrivalent) is safe for pregnant women at any stage of pregnancy and should be administered during any trimester. 1

Recommended Vaccine Type

• Inactivated influenza vaccines (IIV) containing 3 strains (trivalent) or 4 strains (quadrivalent) are the recommended formulations for pregnancy 1
• Recombinant influenza vaccine (RIV) is also considered safe and can be used during pregnancy 1, 2
• Cell culture-based inactivated vaccines (ccIIV) have demonstrated safety in pregnancy based on surveillance data from 2013-2020 and prospective cohort studies 1

Contraindicated Vaccine

Live attenuated influenza vaccine (LAIV), administered intranasally, is absolutely contraindicated during pregnancy due to theoretical risk of placental transmission of the virus to the fetus 1. However, LAIV can be safely used postpartum 1.

Timing of Administration

• Vaccination can be administered during any trimester of pregnancy - there is no need to wait for a specific gestational age 1, 2
• The CDC and WHO recommend one dose of seasonal influenza vaccine during any trimester 1
• Early vaccination (July-August) should be considered for women in their third trimester during these months, as this provides optimal protection for the infant during the first months of life when they are too young to be vaccinated 1
• Vaccination should ideally occur in anticipation of influenza season, but pregnant women should be prioritized to receive the vaccine year-round 1

Safety Evidence

The safety profile is robust and well-established:

• No increased risk of maternal complications or adverse fetal outcomes has been demonstrated with inactivated influenza vaccination 3
• No association with spontaneous abortion (miscarriage) in most studies, including large Vaccine Safety Datalink studies from 2012-2015 1, 3
• No increased risk of stillbirth, preterm birth, small for gestational age, low birth weight, or congenital anomalies 2
• Substantial experience exists with IIV use during pregnancy since 1964, with consistent safety data 4
• Limited but reassuring data exist for first trimester administration specifically 1, 3

Clinical Benefits

Vaccination provides dual protection:

• Reduces risk of laboratory-confirmed influenza infection and hospitalization in pregnant women, who face 7.2% higher hospitalization rates and disproportionately high mortality risk compared to non-pregnant women 1, 2
• Protects infants up to 6 months postpartum through transplacental transfer of maternal IgG antibodies and secretory IgA in breast milk 1, 2
• Pregnant women infected with influenza face significantly increased risk of late pregnancy loss (adjusted HR 10.7) and reduced infant birthweight 1

Important Caveats

• Influenza vaccine can be administered simultaneously with other vaccines, including COVID-19 and pertussis vaccines 2
• Both the American College of Obstetricians and Gynecologists and ACIP strongly recommend influenza vaccination for all pregnant women 1
• Vaccination coverage remains suboptimal at 61.2% in the United States and 1.7%-95% worldwide 1