Flu Vaccine Safety and Pregnancy

Questions & Answers

Note: There is no recommendation that pregnant people or people with pre-existing medical conditions need to get special permission or written consent from their doctor or health care professional for influenza (flu) vaccination if they get vaccinated at a worksite clinic, pharmacy or other location outside of their physician’s office. Pregnant people should not get nasal spray flu vaccine. More information is available at Misconceptions about Seasonal Flu and Flu Vaccines.

Why should pregnant people get a flu shot?

Influenza is more likely to cause illness that results in hospitalization in pregnant people than in people of reproductive age who are not pregnant. Influenza also may be harmful for the developing baby. A common influenza sign, fever, has been associated in some studies with neural tube defects and other adverse outcomes for a developing baby. Getting vaccinated while pregnant also can help protect a baby from influenza after birth (because antibodies are passed to a developing baby during pregnancy). People who get an influenza vaccine while pregnant or breastfeeding also develop antibodies against influenza that they can share with their infants through their breast milk.

A Flu Vaccine is the Best Protection Against Flu

Getting an influenza (flu) vaccine is the first and most important step to protect 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. A 2013 study showed that during the 2010–2011 and 2011–2012 flu seasons vaccination reduced the risk of flu-associated acute respiratory infection in pregnant people by up to one-half. These results are consistent with the general range of estimated flu vaccine effectiveness among adults 18-64 years. 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 vaccine also are helping to protect their babies from flu illness and flu related hospitalizations 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.

Influenza vaccine can be given during any trimester of pregnancy. September and October are generally good times to be vaccinated each year. Earlier vaccination (e.g., in July or August) can be considered for people who are in the third trimester of pregnancy during those months.

Is it safe for pregnant people and their developing babies to get a flu shot?

Yes. Flu shots have been given to millions of people over many years with an excellent safety record. There is a large body of scientific studies that supports the safety of flu vaccine in pregnant people and their babies, and CDC continues to gather data on this topic.

Can flu vaccination result in miscarriage?

Multiple studies have shown that people who have received flu shots during pregnancy have not had a higher risk of spontaneous abortion (miscarriage). One of these studies was conducted using CDC’s Vaccine Safety Datalink (VSD). The study covered three flu seasons (2012-13, 2013-14, 2014-15) looking for any increased risk for miscarriage among pregnant people who had received a flu vaccine during their pregnancy. The study found no increased risk for miscarriage after flu vaccination during pregnancy. This study was conducted as a follow-up to a previous smaller study. The prior study examined data from the 2010-2011 and 2011-2012 flu seasons and identified an association between flu vaccination early in pregnancy and spontaneous abortion (miscarriage), particularly among people who had received flu vaccine during the previous flu season. However, the smaller study had several limitations, including small sample size, which could have led to imprecise results. This study was the only analysis to show that association; no other studies had found an increased risk of miscarriage following flu vaccination. The Advisory Committee on Immunization Practices (ACIP), the American College of Obstetricians and Gynecologists (ACOG) and CDC recommend that pregnant people get a flu vaccine during any trimester of their pregnancy because flu poses a danger to pregnant people and a flu vaccine can prevent serious illness, including hospitalization, during pregnancy.

A fact sheet with more information on this topic is available. Any pregnant person who has questions about vaccines should talk to their health care provider.

What side effects have pregnant people experienced from flu shots?

The most common side effects experienced by pregnant people are the same as those experienced by other people. They are generally mild and include:

  • Soreness, redness, and/or swelling from the shot
  • Headache
  • Fever
  • Muscle aches
  • Nausea
  • Fatigue

If side effects occur, they usually begin soon after the shot is given and generally last for 1-2 days.

A flu shot, like other injections, can occasionally cause fainting. Rarely, flu shots can cause serious problems like severe allergic reactions. Anyone with a severe, life-threatening allergy to any of the vaccine ingredients should not get the shot.

Who should not get a flu shot?

Anyone with a severe, life-threatening allergy to any of the ingredients or components of a particular vaccine (other than egg protein) should not get that vaccine. People who have had a severe, life-threatening allergic reaction to a previous dose of an influenza vaccine should generally not be vaccinated, depending upon what kind of influenza vaccine caused the allergic reaction. It is important to discuss allergies that you have (such as allergies to medications or vaccines and other allergies) with your health care provider.

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Can pregnant people with egg allergies get vaccinated?

Pregnant people with egg allergies of any severity may get any flu shot (egg-based or non-egg-based) that is otherwise appropriate for their age and health status. The nasal spray flu vaccine (LAIV4) should not be used during pregnancy. Previously, it was recommended that people with severe allergy to egg (those who have had any symptom other than hives with egg exposure) be vaccinated in an inpatient or outpatient medical setting. Beginning with the 2023-2024 season, additional safety measures are no longer recommended for flu vaccination of people with an egg allergy beyond those recommended for receipt of any vaccine, regardless of the severity of previous reaction to egg. All vaccines should be given in settings where allergic reactions can be recognized and treated quickly.

Vaccine Effectiveness

Influenza (flu) vaccine effectiveness (VE) can vary. The protection provided by a flu vaccine varies from season to season and depends in part on the age and health status of the person getting the vaccine and the similarity or “match” between the viruses in the vaccine and those in circulation. During years when the flu vaccine match is good, it is possible to measure substantial benefits from flu vaccination in terms of preventing flu illness and complications. However, the benefits of flu vaccination will still vary, depending on characteristics of the person being vaccinated (for example, their health and age), what flu viruses are circulating that season and, potentially, which type of flu vaccine was used. More information is available at Vaccine Effectiveness – How well does the Flu Vaccine Work.

How is the safety of flu vaccines in pregnant people monitored?

CDC and FDA conduct ongoing safety monitoring of vaccines licensed for use in the United States.

CDC and FDA monitor flu vaccine safety during pregnancy during each flu season using the Vaccine Adverse Event Reporting System (VAERS): an early warning system that helps CDC and FDA monitor for health concerns (also termed “adverse events”) following vaccination. Anyone can report adverse events after vaccination to VAERS. Generally, information from VAERS reports cannot determine if an adverse event after vaccination was caused by a vaccine, but these reports can help indicate if further investigations are needed.

In addition CDC conducts research studies in the Vaccine Safety Datalink (VSD): A collaboration between CDC and nine health care organizations which allows ongoing monitoring and proactive searches of vaccine-related data.

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What studies has CDC conducted on flu vaccine safety during pregnancy?

Several studies conducted by CDC and partners support the safety of the flu vaccine for pregnant people and their babies.

  1. Review of reports to the Vaccine Adverse Reporting System (VAERS) (Moro et al, 2011, Moro et al, 2011, Moro et al, 2017) found no evidence to suggest a link between pregnancy complications or adverse fetal outcomes among pregnant women and flu shots.
  2. A large study using VSD data from three flu seasons (2012-13, 2013-14, 2014-15) found no increased risk for spontaneous abortion after flu vaccination during pregnancy. A similar study using VSD data (Irving et al, 2013) from the 2005-06 and 2006-07 seasons also found no increased risk of miscarriage among pregnant people who received flu vaccines. One study of the 2010-2012 flu seasons, however, found that people in early pregnancy who received two consecutive annual flu vaccines had an increased risk of miscarriage in the 28 days after receiving the second vaccine. A limitation of this study was its small sample size which could have led to imprecise results. In response to the findings from the 2010-2012 flu season study, CDC provided funding for the larger follow-up VSD study conducted during the 2012-2015 flu seasons that included about three times as many people and found no association between flu vaccination and miscarriage. More information on this topic is available at Addressing Concerns Pregnant People Might Have about Influenza Vaccine Safety | CDC.
  3. A large study using VSD data (Kharbanda et al, 2013) found no increased risk for adverse obstetric events (like chorioamnionitis, pre-eclampsia, or gestational hypertension) for pregnant people who received the flu vaccine from 2002 to 2009 when compared to pregnant people who were not vaccinated.
  4. A VSD study (Nordin et al, 2014) compared pregnant people who received the flu shot with an equal number of pregnant people who did not receive the flu shot during the 2004-05 and 2008-09 flu seasons. The study found no differences between the two groups in the rates of premature delivery or small for gestational age infants.
  5. A large August 2017 study using VSD data found that the babies of people who received the flu shot during their first trimester had no increased risk of having children with major birth defects.
  6. A VSD study (Panagiotakopoulos et al 2020) examined stillbirth rates in pregnant persons aged 14-49 years between 2007 and 2015 and did not find a significant association between influenza vaccination during pregnancy and stillbirth.

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Where should a pregnant person get vaccinated?

There are many different options for pregnant people to receive a flu shot, including a health care provider’s office, at work, a pharmacy, some stores, or a supermarket. All these places give flu vaccines that are licensed and approved for use in the United States. If you’ve never had a problem when previously receiving a flu vaccine, then there is no reason you can’t get a flu vaccine at work or a supermarket.

What about thimerosal in flu vaccines? Should pregnant people get thimerosal-free flu vaccines?

Studies have shown the small amount of thimerosal in vaccines does not cause harm. There is thimerosal-free flu vaccine available for people who want to avoid thimerosal. More information about thimerosal can be found at Thimerosal and Flu Vaccines

Can a breastfeeding person get a flu vaccine?

Yes. People who are breastfeeding should get an annual flu vaccine to protect themselves from flu. Getting vaccinated reduces parents’ risk of getting sick and of passing the flu on to their babies, thus protecting their babies from flu also. his is especially important for children younger than 6 months old since they are too young to receive flu vaccine themselves. People who get the flu vaccine while pregnant or breastfeeding also develop antibodies against flu that they can share with their infants through their breast milk.