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Seasonal Flu Vaccine Safety and Pregnant Women

Questions & Answers

Influenza is more likely to cause severe illness in pregnant women than in women who are not pregnant. Changes in the immune system, heart, and lungs during pregnancy make pregnant women more prone to severe illness from influenza as well as hospitalizations and even death. Pregnant women with influenza also have a greater chance for serious problems for their unborn babies, including premature labor and delivery.

Why should pregnant women get the seasonal flu vaccine?

Pregnant women have a higher risk for serious complications from influenza than non-pregnant women of reproductive age. Influenza vaccine will protect pregnant women, their unborn babies, and protect the baby after birth against the flu.

To prevent influenza and complications in pregnant women, in 2004 the Centers for Disease Control and Prevention's (CDC) Advisory Committee on Immunization Practices (ACIP) began recommending routine immunization of pregnant women with the flu shot at any stage of pregnancy. The nasal spray vaccine is not recommended for use in pregnant women. More information, see ACIP recommendations for influenza vaccination during the 2014-2015 season.

Is it safe for pregnant women to get seasonal flu vaccine?

Yes. The seasonal flu shot has been given safely to millions of pregnant women over many years. Flu shots have not been shown to cause harm to pregnant women or their babies.

Can a breastfeeding mother get the flu shot or the nasal spray?

Yes. Seasonal flu vaccines should be given to breastfeeding mothers and breastfeeding women can get either the flu shot or the nasal spray form of the vaccine. Breastfeeding is fully compatible with flu vaccination, and preventing the flu in mothers can reduce the chance that the infant will get the flu. This is especially important for infants younger than 6 months old, since they are too young to be vaccinated.

What research shows that seasonal flu vaccine is safe for unborn babies?

Studies of several thousand pregnant women in scientific literature have assessed the safety of using the flu vaccine during pregnancy. These studies have shown no evidence of harm to pregnant women, to the unborn child (or fetus) or to newborns of vaccinated women. In fact, studies have shown that vaccinating a pregnant woman can give her baby antibodies to protect against flu for six months after they are born. In addition, the Food and Drug Administration's (FDA) and CDC's routine monitoring of adverse events has not raised safety concerns.

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What side effects have pregnant women experienced from the seasonal flu shot?

The most common side effects after flu shots experienced by pregnant women are the same as for other people. These are mostly mild, such as soreness and tenderness and/or redness and swelling where the shot was given. Some people might have headache, muscle aches, fever, and nausea or feel tired. If these problems happen, they usually begin soon after the shot is given and may last as long as 1-2 days. Some people may faint after getting any shot. Sometimes, flu shots can cause serious problems like severe allergic reactions. But, life-threatening allergic reactions to vaccines are very rare. Most people person who have an allergy to eggs can get vaccinated, with some additional safety measures (link). A person with severe (life-threatening) allergy to anything else in the vaccine 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.

What studies has CDC conducted on adverse events in pregnant women who received seasonal flu vaccine?

In 2011, CDC and FDA conducted a search of reports to the Vaccine Adverse Event Reporting System (VAERS) of pregnant women who received seasonal influenza vaccines from 1990 to 2009 to assess potential vaccine safety concerns. The results of this study were recently published in the American Journal of Obstetrics and Gynecology.

Overall, the study concluded that no unusual patterns of pregnancy complications or adverse fetal outcomes were observed in the VAERS reports of pregnant women after being given the flu shot or nasal spray flu vaccine (while the nasal spray is not recommended for pregnant women, scientists were reassured to find that the inadvertent administration of this vaccine to pregnant women did not result in reported unexpected reactions). Data from CDC's 19-year review of VAERS add to an existing body of evidence supporting the safety of the flu shot for pregnant women.

CDC also is conducting studies of flu vaccine safety and pregnancy through the Vaccine Safety Datalink (VSD). The results of a VSD study of flu vaccine and spontaneous abortions were published in the American Journal of Obstetrics and Gynecology. The study provides reassuring findings that flu vaccine given to pregnant women during the first trimester of pregnancy does not increase the risk of spontaneous abortion. Another large study in the VSD compared risks for adverse obstetric events (e.g. chorioamnionitis, pre-eclampsia, gestational hypertension) between 74,292 pregnant women who received the flu shot and 144,597 who were not vaccinated. No increased risks for adverse obstetric events were found. Findings of this study were published in Obstetrics and Gynecology in 2013 (1). A second study of the same group of pregnant women found that the flu shot was not associated with increased risk of allergic reactions, cellulitis, and certain neurological conditions (seizures, Guillain-Barré syndrome, optic neuritis, transverse myelitis, or Bells palsy) (2). A third study in the VSD compared 57,554 pregnant women who received the flu shot with an equal number of unvaccinated pregnant women during the 2004-2005 and 2008-2009 influenza seasons and found that it was not associated with an increased or decreased risk of premature delivery or small for gestational age infants. This study was recently published in the Journal of Pediatrics in 2014 (3).

How is the safety of the 2014-2015 seasonal flu vaccine being monitored?

CDC and FDA conduct ongoing monitoring of the safety of seasonal influenza and other vaccines licensed for use in the United States, in cooperation with state and local health departments, health care providers, and other partners. Monitoring the safety of seasonal flu vaccine in pregnant women is part of this effort.

Two main systems being used to monitor flu vaccine safety are VAERS, which is jointly operated with FDA, and the Vaccine Safety Datalink (VSD) Project, managed and coordinated by CDC's Immunization Safety Office. Other systems are also being used. Through vaccine safety monitoring, CDC and FDA are able to quickly identify any clinically significant adverse events following immunization that warrant further study or action to protect the health of the public.

More information on Pregnant Women & Influenza (Flu).

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References

  1. Kharbanda EO, Vazquez-Benitez G, Lipkind H, Naleway A, Lee G, Nordin JD; Team., Vaccine Safety Datalink. “Inactivated influenza vaccine during pregnancy and risks for adverse obstetric events.” Obstet Gynecol. 2013 Sep. 122(3):659-67
  2. Nordin JD, Kharbanda EO, Benitez GV, Nichol K, Lipkind H, Naleway A, Lee GM, Hambidge S, Shi W, Olsen A. “Maternal safety of trivalent inactivated influenza vaccine in pregnant women.” Obstet Gynecol. 2013 Mar. 121(3):519-25
  3. Nordin JD, Kharbanda EO, Vazquez Benitez G, Lipkind H, Vellozzi C, Destefano F; Datalink, Vaccine Safety. “Maternal influenza vaccine and risks for preterm or small for gestational age birth.” Journal of Pediatrics. 2014 May. 164(5):1051-1057.e2
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Note: There is no recommendation for pregnant women or people with pre-existing medical conditions to seek special permission or secure written consent from their doctor for influenza vaccination if they get vaccinated at a worksite clinic, pharmacy or other location outside of their physician's office. For more information, visit Misconceptions about Seasonal Flu and Flu Vaccines.

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