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 make people more susceptible to influenza severe enough to cause hospitalization throughout pregnancy and up to two weeks postpartum. Influenza also may be harmful for the developing baby. A common influenza symptom fever may be associated with neural tube defects and other adverse outcomes for a developing baby. Parental vaccination also can help protect a baby from influenza after birth (because antibodies are passed to a developing baby during pregnancy).

A Flu Vaccine is the Best Protection Against Flu

Getting an influenza (flu) vaccine is the first and most important step in protecting against flu. Pregnant people should get a flu shot and not the nasal spray flu vaccine. Flu shots given during pregnancy help protect both the pregnant parent and the baby from flu. Vaccination has been shown to reduce the risk of flu-associated acute respiratory infection in pregnant people by up to one-half. A 2018 studyexternal icon showed that getting a flu shot reduced a pregnant person’s risk of being hospitalized with flu by an average of 40 percent. Pregnant people who get a flu vaccine 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 on the benefits of flu vaccination for pregnant people is available.

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 months of life (when they are too young to be vaccinated).  Some children need 2 doses given at least 4 weeks apart (children 6 months through 8 years of age who either have never received flu vaccine, or who have not already received a total of at least 2 doses in their lives).  These children should get their first dose soon after vaccine is available, so that they can receive the second dose (which has to be given at least 4 weeks after the first) by the end of October.

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 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

CDC’s Vaccine Safety Datalink (VSD) project conducted one of the largest studies examining influenza vaccination and risk of miscarriage. The studyexternal icon 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 the larger study support current ACIP policy recommending influenza vaccination at any time during pregnancy. Earlier Studies That Support the Safety of Influenza Vaccination in Pregnant People.

Earlier Studies That Support the Safety of Influenza Vaccination in Pregnant People
  1. Reviews of reports to the Vaccine Adverse Reporting System(VAERS) (Moro et al, 2011external icon and Moro et al, 2017external icon) 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, 2013external icon) 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, 2013external icon) 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, 2014external icon) 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 dataexternal icon found that the babies of people vaccinated during their first trimester had no increased risk of major birth defects.