Pregnant Women Should Receive the Flu Shot
Yes, pregnant women can and should receive the inactivated influenza vaccine during any trimester of pregnancy. 1, 2
Strong Recommendation from Major Guidelines
The Advisory Committee on Immunization Practices (ACIP) and the American College of Obstetricians and Gynecologists (ACOG) both strongly recommend that all women who are or will be pregnant during influenza season receive the inactivated influenza vaccine (IIV). 1, 3 This recommendation is based on:
Increased maternal risk: Pregnant women face higher risk for severe illness, complications, hospitalization, intensive care unit admission, and death from influenza compared to non-pregnant women, particularly during the second and third trimesters. 1, 2, 3
Dual protection benefit: Vaccination protects both the mother and her infant through transplacental antibody transfer during pregnancy and continued protection through breastfeeding after birth. 1, 4, 2
Infant protection: Infants born to vaccinated mothers have a 72% risk reduction for laboratory-confirmed influenza hospitalization in their first months of life, when they are too young to receive their own vaccination. 4, 5
Timing and Administration
The vaccine can be administered at any time during pregnancy—during any trimester—before and during the influenza season. 1, 2, 3
Ideally, vaccination should occur by the end of October when vaccine becomes available, but vaccination throughout the influenza season is encouraged. 4, 3
For women in their third trimester during July-August, early vaccination can be considered to provide protection for the infant during the first months of life. 1
Critical Vaccine Type Distinction
Only inactivated influenza vaccine (IIV) or recombinant influenza vaccine (RIV4) should be used during pregnancy. 1, 2
Live attenuated influenza vaccine (LAIV/nasal spray) is contraindicated during pregnancy due to theoretical risk of placental transmission of live virus to the fetus. 1, 2
Postpartum women can receive either IIV or LAIV. 1
Any licensed, recommended, and age-appropriate IIV4 or RIV4 may be used during pregnancy. 1
Safety Profile
The safety data for influenza vaccination during pregnancy is substantial and reassuring:
Most studies have not found an association between influenza vaccination and adverse pregnancy outcomes, including spontaneous abortion. 1, 6
One observational study from 2010-11 and 2011-12 seasons noted an association between IIV containing H1N1pdm09 and miscarriage risk in the 28 days after vaccination when H1N1pdm09-containing vaccine was also received the previous season. 1
However, a larger follow-up study found no increased risk for miscarriage during 2012-13,2013-14, and 2014-15 seasons, regardless of previous season vaccination. 1
No study to date has demonstrated increased risk of maternal complications or adverse fetal outcomes associated with inactivated influenza vaccination. 6
The vaccine is classified as Pregnancy Category C by the FDA, but this reflects limited formal studies rather than evidence of harm. 7
Clinical Benefits Beyond Maternal Protection
Vaccination during pregnancy provides multiple layers of protection:
Transplacental antibody transfer: IgG antibodies cross the placenta, providing passive immunity to the newborn. 4, 2
Breastmilk antibody transfer: Vaccinated mothers produce breast milk with higher levels of influenza-specific IgA antibodies. 4
Reduced infant respiratory illness: Greater exclusivity of breastfeeding in the first 6 months decreases episodes of respiratory illness with fever in infants of vaccinated mothers. 4
Common Pitfalls to Avoid
Do not delay vaccination waiting for a specific trimester—it can be given safely during any trimester. 1, 2, 3
Do not use the nasal spray (LAIV) during pregnancy—only inactivated or recombinant vaccines are appropriate. 1, 2
Do not avoid vaccination due to concerns about first trimester safety—the evidence supports safety throughout pregnancy. 1, 6
Do not miss the opportunity to vaccinate during prenatal visits—provider recommendation is the strongest predictor of vaccination uptake. 8, 3
Provider Role is Critical
Healthcare providers play an essential role in achieving adequate vaccination coverage:
Women offered influenza vaccination by a healthcare provider are significantly more likely to be vaccinated (71%) compared to those not offered vaccination (14%). 8
Obstetrician-gynecologists should stock and administer the influenza vaccine in their offices, or refer patients to another provider, pharmacy, or vaccination center if unable to provide it directly. 3
Provider endorsement and strong recommendation are major factors in patient acceptance and vaccine uptake. 1, 3