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Flu Vaccine Safety and Pregnancy

Questions & Answers

Why should pregnant women get a flu shot?

Flu is more likely to cause severe illness in pregnant women than in healthy women who are not pregnant. Changes in the immune system, heart, and lungs during pregnancy make pregnant women (and women who have recently given birth) more prone to severe illness from flu, as well as to hospitalizations and even death. Getting the flu during pregnancy also raises the risks of pregnancy complications, including premature labor and delivery. Studies have shown that vaccinating a pregnant woman can pass antibodies on to the baby that will protect against flu for six months after birth.

CDC recommends that pregnant women get a flu shot during any trimester of their pregnancy to protect themselves, their unborn babies, and their newborn babies from flu. The nasal spray vaccine is not recommended for use in pregnant women. To learn more about flu and pregnant women, please visit Pregnant Women & Influenza (Flu).

Is it safe for pregnant women and their unborn babies to get a flu shot?

Yes. The flu shot has been given safely to millions of pregnant women over many years. There is a large body of scientific studies that supports the safety of flu vaccine in pregnant women and their babies. The CDC continues to gather data on this topic.

What side effects have pregnant women experienced from flu shots?

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

  • Soreness, redness, and/or swelling from the shot
  • Fainting
  • 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.

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.

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Can pregnant women with egg allergies get vaccinated? 

Most people who have an allergy to eggs can get vaccinated, with some additional safety measures. A person with severe (life-threatening) allergy to any vaccine component, including egg protein, should not get the shot, even if she is pregnant. Pregnant women should tell the person giving the shots if they have any severe allergies or if they have ever had a severe allergic reaction following a flu shot.

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

CDC and FDA conduct ongoing safety monitoring of all vaccines licensed for use in the United States. CDC and FDA use two primary systems to monitor flu vaccine safety during pregnancy: 

  1. Vaccine Adverse Event Reporting System (VAERS): An early warning system that helps CDC and FDA monitor problems following vaccination.  Anyone can report possible vaccine side effects to VAERS. Generally, VAERS reports cannot determine if a health concern that arises after vaccination (adverse event) was caused by a vaccine, but these reports can help indicate if further investigations are needed.
  2. Vaccine Safety Datalink (VSD): A collaboration between CDC and nine health care organizations which allows ongoing monitoring and proactive searches of vaccine-related data.
  3. These two systems, along with other systems, are used to quickly identify if there are any health problems after flu vaccination during pregnancy that should be studied further, or if any actions are needed.

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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 women and their unborn babies.

  1. A review of reports to the Vaccine Adverse Reporting System (VAERS) (Moro et al, 2011) found no link between pregnancy complications or adverse fetal outcomes among pregnant women and flu shots or nasal spray flu vaccine.
    • While the nasal spray is not recommended for pregnant women, researchers were reassured to find that the accidental administration of the nasal spray vaccine to pregnant women did not result in any complications.
  2. A study using Vaccine Safety Datalink (VSD) data (Irving et al, 2013) found no increased risk of miscarriage among pregnant women who received flu 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 (like chorioamnionitis, pre-eclampsia, or gestational hypertension) for pregnant women who received the flu vaccine from 2002 to 2009 when compared to pregnant woman who were not vaccinated.  
  4. A VSD study (Nordin et al, 2014) compared pregnant women who received the flu shot with an equal number of pregnant women who did not receive the flu shot during the 2004-05 and 2008-09 flu seasons, and found no differences between the two groups in the rates of premature delivery or small for gestational age infants.

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Where should a pregnant woman get vaccinated?

There are many different options for pregnant women to receive the flu shot, including a health care provider’s office, at work, a store, 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, a store, or a supermarket.

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

Several 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 women get a flu vaccine?

Yes. Breastfeeding women should get the flu vaccine to protect themselves from flu. Getting vaccinated reduces  mothers’ risk of getting sick and of passing the flu on to their babies, thus protecting them from flu also. This is especially important for children younger than 6 months old since they are too young to be vaccinated themselves. Breastfeeding women can get either a flu shot or nasal spray vaccine.  

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