Flu Vaccine In Pregnancy: Its Benefits And Safety Concerns

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Getting an influenza or flu vaccine in pregnancy protects against influenza viruses. Influenza viruses cause contagious respiratory illness, putting an infected mother at risk of severe illness and fatal complications due to a naturally suppressed immunity.

Besides, the infection can pass to the baby, increasing the risk of congenital disabilities, especially if the mother has contracted the flu just before or during early pregnancy. Hence, mothers should get vaccinated against influenza irrespective of the gestation stage (1).

Keep reading to learn if the influenza vaccine is safe during pregnancy and its benefits for the mother and baby.

Is It Safe To Get A Flu Shot During Pregnancy?

Yes, there are several scientific studies to prove the safety of the flu shot during pregnancy. Both the Centers for Disease Control and Prevention (CDC) and the American College of Obstetricians and Gynecologists (ACOG) recommend that women who are or plan to be pregnant during the flu season should receive an inactivated influenza vaccine (2). However, the CDC does not recommend the nasal spray vaccine during pregnancy as it comprises weakened but live viruses (3).

Why Are Pregnant Women At Higher Risk Of Serious Flu Illness?

Pregnancy brings complex modulation to your immune system. Additionally, organs, such as the heart and lungs, need to cope with the extra requirements of the progressing pregnancy. So it is possible that the body will not be able to combat influenza as efficiently as earlier, even if you are otherwise healthy and strong (4) (5).

How Effective Is The Flu Shot?

A flu shot provides protection to both the mother and baby from the adverse outcomes of influenza. Studies have shown about 40% reduced risk of hospitalization in pregnant women who were vaccinated. Additionally, the CDC states that there is no significant link of spontaneous abortion (miscarriage) with influenza vaccination in pregnant women. On the contrary, severe maternal illness due to the flu increases the risk of fetal problems, including neural tube defects, premature labor, and even stillbirth (6) (7).

Scientific evidence claims that maternal immunization can reduce the risk of preterm birth and stillbirth. The antibodies produced in the mother’s body after vaccination are passed on to the baby in the uterus and via breast milk after birth. This provides immunity to the baby for the first few months of life. This is important because babies under six months cannot get the flu vaccine.

The CDC mentions September and October as ideal periods for vaccination. However, those in their third trimester of pregnancy can opt for an earlier time. This allows even the newborn to be protected with the mother (3) (8).

Are There Any Side Effects Of The Flu Shot In Pregnant Women?

The common side effects of the influenza vaccine may include (9):

  • Pain at the injection site
  • Mild fever
  • Body pain
  • Tiredness

Who Should Not Get The Flu Shot?

The vaccine cannot be given to people with severe life-threatening allergic reactions to egg proteins. However, those with mild egg allergies, such as hives, can be vaccinated. If egg allergy causes other symptoms, such as swelling, difficulty in breathing, lightheadedness, or recurrent vomiting, they should be vaccinated in a medical setting under the supervision of a healthcare provider competent in managing allergic reactions (2).

Frequently Asked Questions

1. Is there any danger of catching the flu from the flu vaccine?

No, you cannot catch the flu from the vaccine. Flu shots (injected using a needle) contain the killed virus or a single protein from the influenza virus that cannot cause illness (10).

2. Does the flu vaccine contain thimerosal?

Thimerosal is a mercury-containing preservative used to prevent contamination of vaccines after multidose vials are opened. Single-dose vials often do not contain this chemical or contain trace amounts. Studies have not found any known harm from thimerosal-containing influenza vaccines. Thus, both preservative-free or thimerosal-containing flu vaccines may be used in pregnant women (9).

Influenza is a very common and highly infectious viral disease. It usually causes fever, cough, sore throat, and runny nose but may lead to serious illness during pregnancy (11). It is always better to prevent flu infection than treat it with antivirals during pregnancy. The seasonal influenza vaccine before or early in pregnancy is a safe and effective option to reduce the risk of adverse outcomes from the flu for both mother and baby.

Key Pointers

  • Flu shots are safe during pregnancy since they reduce the risk of catching the flu.
  • The antibodies from the mother reach the baby through the blood and breastmilk after birth, thus strengthening fetal immunity.
  • Some common side effects of the flu shot are mild fever, body ache, and fatigue.
  • Flu shots must be taken under medical supervision.

References:

MomJunction's articles are written after analyzing the research works of expert authors and institutions. Our references consist of resources established by authorities in their respective fields. You can learn more about the authenticity of the information we present in our editorial policy.
  1. The flu jab in pregnancy.
    https://www.nhs.uk/pregnancy/keeping-well/flu-jab/
  2. Influenza Vaccination During Pregnancy.
    https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2018/04/influenza-vaccination-during-pregnancy
  3. Flu Vaccine Safety and Pregnancy.
    https://www.cdc.gov/flu/highrisk/qa_vacpregnant.htm#studies
  4. Gil Mor and Ingrid Cardenas, The immune system in pregnancy: a unique complexity.
    https://pubmed.ncbi.nlm.nih.gov/20367629/
  5. Influenza (Flu) Vaccine and Pregnancy.
    https://www.cdc.gov/vaccines/pregnancy/hcp-toolkit/flu-vaccine-pregnancy.html
  6. Influenza (flu) vaccine in pregnancy.
    https://www.healthywa.wa.gov.au/Articles/F_I/Influenza-vaccine-in-pregnancy-What-expectant-mothers-need-to-know
  7. Michelle L. Giles et al.; (2021); Associations Between Maternal Immunisation and Reduced Rates of Preterm Birth and Stillbirth: A Population Based Retrospective Cohort Study.
    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8454544/
  8. Mark G Thompson et al.; (2018); Influenza Vaccine Effectiveness in Preventing Influenza-associated Hospitalizations During Pregnancy: A Multi-country Retrospective Test Negative Design Study, 2010–2016.
    https://academic.oup.com/cid/article/68/9/1444/5126390
  9. Use of Influenza A (H1N1) 2009; Monovalent Influenza Vaccine in Pregnant Women.
    https://www.fda.gov/vaccines-blood-biologics/vaccines/use-influenza-h1n1-2009-monovalent-influenza-vaccine-pregnant-women
  10. Misconceptions about Seasonal Flu and Flu Vaccines.
    https://www.cdc.gov/flu/prevent/misconceptions.htm?CDC_AA_refVal=https%3A%2F%2Fwww.cdc.gov%2Fflu%2Fabout%2Fqa%2Fmisconceptions.htm
  11. Pregnancy and the flu.
    https://medlineplus.gov/ency/article/007443.htm
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Dr. Mona Hardas

(MD)
Dr. Mona Hardas is a practicing Ob/Gyn from Flint, Michigan, with over 20 years of experience in private practice. She is also actively involved in teaching medical students and residents as an associate clinical professor from MSU College of Human Medicine.  Dr. Hardas is interested in minimally invasive gynecology procedures, including laparoscopic hysterectomy, myomectomy, removal of adnexal masses, etc. Having... more

Dr. Joyani Das

Dr. Joyani Das is a PhD in Pharmacology with over two years of experience in academics. Previously, she worked as an associate professor, faculty of Pharmacology. With her research background in preclinical studies and a zeal for scientific writing, she joined MomJunction as a health writer. Her research work was published in international journals and publications, such as Elsevier, Current... more