Addressing Concerns Pregnant People Might Have about Influenza Vaccine Safety

Information & Guidance for Health Care Providers

Health care providers for pregnant people play a vital role in advising their patients on how to protect themselves and their developing babies against many threats, including influenza. This page contains information about influenza and influenza vaccination during pregnancy and provides guidance on how to address concerns that patients may have about influenza vaccination.

Background

Influenza is more likely to cause severe illness in pregnant people than in people of reproductive age who are not pregnant. Changes to the immune system, heart, and lungs during pregnancy may make people more prone to influenza severe enough to cause hospitalization. Influenza also may be harmful for the developing baby. A common influenza symptom can be fever, which may be associated with neural tube defects and other adverse outcomes for a developing baby.  Vaccination during pregnancy also can help protect a baby from influenza after birth (because antibodies are passed from the pregnant parent to the developing baby during pregnancy).

A Flu Vaccine is the Best Protection Against Flu

Getting a flu vaccine is the first and most important action a person can take to protect against flu and its potentially serious complications. Pregnant people should get a flu shot and not the nasal spray flu vaccine. Vaccination has been shown to reduce the risk of flu in pregnant people by up to 50% . A 2018 study showed that getting a flu shot reduced a pregnant person’s risk of being hospitalized with flu by an average of 40%. Pregnant people who get a flu shot also are helping to protect their babies from flu illness for the first several months after their birth, when they are too young to get vaccinated. A list of recent studies is available at benefits of flu vaccination for pregnant people. September and October are generally good times to be vaccinated. Early vaccination also can be considered for people who are in the third trimester of pregnancy, because this can help protect the baby after birth during their first several months of life (when they are too young to be vaccinated).

The CDC’s Advisory Committee on Immunization Practices and the American College of Obstetricians and Gynecologists recommend that all adults receive an annual influenza vaccine and that people who are or will be pregnant during influenza season receive an inactivated influenza vaccine (pregnant people should not receive a live attenuated influenza vaccine) as soon as it is available. Millions of doses of influenza vaccines have been administered safely for more than 75 years, including to pregnant people. The safety of influenza vaccination during pregnancy has been consistently demonstrated by numerous clinical trials, observational studies, and data from safety reporting systems.

Getting an Influenza Vaccine While Pregnant Does Not Increase the Risk of Miscarriage or Stillbirth

CDC’s Vaccine Safety Datalink (VSD) project conducted one of the largest studies examining influenza vaccination and risk of miscarriage. The study covered three influenza seasons (2012–13, 2013–14, 2014–15), looking for any increased risk for miscarriage among those who had received an influenza vaccine during their pregnancy. The study found no increased risk of miscarriage associated with influenza vaccination during pregnancy. This study was a follow-up to a previous smaller study that suggested pregnant people who received H1N1-containing flu vaccine two years in a row might have an increased risk of miscarriage. The more recent results from this larger study showed that flu vaccination was safe for pregnant people and their unborn babies and support the current ACIP recommendation for flu vaccination at any time during pregnancy. Another study in the VSD (Panagiotakopoulos et al. 2020) examined the risk of stillbirths (fetal deaths occurring after 20 weeks gestation) among pregnant women who received an influenza vaccine and found no increased risk of this event among influenza vaccine recipients.

Earlier Studies That Support the Safety of Influenza Vaccination in Pregnant People include:
  1. Reviews of reports to the Vaccine Adverse Event Reporting System(VAERS) (Moro et al, 2011and Moro et al, 2017 found no unusual or unexpected patterns of pregnancy complications or adverse fetal outcomes associated with influenza vaccines.
  2. A study using VSD data (Irving et al, 2013) found no increased risk of miscarriage among pregnant people who received influenza vaccines in the 2005–06 or 2006–07 flu seasons.
  3. A large study using VSD data (Kharbanda et al, 2013) found no increased risk for adverse obstetric events such as chorioamnionitis, pre-eclampsia, or gestational hypertension among pregnant people who received an influenza vaccine from 2002 to 2009 when compared to pregnant those who were not vaccinated.
  4. A VSD study (Nordin et al, 2014) compared pregnant people who received an influenza vaccine during the 2004-05 and 2008-09 flu seasons with an equal number who did not. The study found that rates of premature delivery or small for gestational age infants were the same for both groups
  5. A large August 2017 study using VSD data found that the babies of people vaccinated during their first trimester had no increased risk of major birth defects.