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No Connection Between H1N1 Flu Vaccine and Autism, Study Finds

pregnant woman getting vaccine

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Key Takeaways

  • Some pregnant women opt out of getting the flu shot due to the incorrect belief that the vaccine could cause their unborn baby to develop autism in the future.
  • A new study finds no connection between the H1N1 flu vaccine and autism in unborn babies.
  • The H1N1 vaccine is separate from the regular yearly flu shot.

The COVID-19 public health crisis will make vaccines more important than ever before, especially for pregnant women. A groundbreaking recent study published in the Annals of Internal Medicine found that getting a flu shot during pregnancy does not increase an unborn baby’s chances of developing autism.

Public health experts unanimously agree that the annual flu shot is a critical component of prenatal care. That’s because the flu is more deadly for pregnant women and unborn babies alike.

According to the American College of Obstetrics and Gynecology, “In addition to hospitalization, pregnant women with influenza are at increased risk of intensive care unit admission and adverse perinatal and neonatal outcomes.” 

The Importance of Flu Shots During Pregnancy

Pregnant women of all ages, regardless of their current stage of pregnancy, should receive flu shots as soon as they become available each year. Yet only about half do, according to a 2019 report by the CDC. One of the biggest concerns moms-to-be cite when avoiding vaccinations is fear of their unborn child developing complications, including autism. 

It’s a fear that’s been circulating since an unfounded study was published in 1997 pointing the finger at thimerosal, a mercury-based vaccine preservative. But the 2020 study asserts that babies whose mothers received the flu vaccine during pregnancy are no more likely to develop autism than babies who weren’t exposed to the vaccine.

The large-group study focused specifically on the H1N1 flu strain, and followed more than 69,000 babies, 39,726 of whom were exposed to the H1N1 flu vaccine in utero, and 29,293 who weren’t.

What is H1N1? 

H1N1 is a strain of the flu. Most strains of the flu share similarities when it comes to symptoms people experience and how contagious the virus is. And that holds true for the H1N1 strain, commonly known as “swine flu.”

It’s not known to be any more severe or deadly than the regular flu. But it has its own vaccine due to the 2009 H1N1 pandemic that swept the nation, sickening more than 60 million people and causing over 12,000 deaths in a single flu season.

What is the H1N1 vaccine?

The H1N1 vaccine is a variation of the regular annual flu shot that contains the novel 2009 swine flu strain, H1N1. It’s manufactured the same way and is considered just as safe and effective as the regular flu shot.

A regular flu shot combines several different strains of flu based on which ones scientists believe are most likely to circulate in a given year. Health experts recommend that people receive flu vaccinations each year.

Can the H1N1 vaccine cause autism? 

Definitely not, says Kim Langdon, an OB-GYN with Medzino. “For years, there has been no lack of hysteria and misinformation regarding vaccines of any type and autism," she says. "Hundreds, if not thousands, of research articles have failed to find a link between vaccines and the occurrence of autism.” 

Kim Langdon, MD

For years there has been no lack of hysteria and misinformation regarding vaccines of any type and autism. Hundreds, if not thousands, of research articles have failed to find a link between vaccines and the occurrence of autism.

— Kim Langdon, MD

And the recent study agrees. Of the nearly 40,000 vaccine-exposed babies who participated in the study, 394 went on to develop autism or an autistic spectrum disorder. That’s an incidence rate of 1.0%, says Langdon. “Compare that to the 1.1% of non-vaccine exposed babies who went on to develop autism or a spectrum disorder, and it’s easy to see that there’s simply no established link between the H1N1 vaccine and autism.” 

How will COVID affect this year’s flu season? 

While COVID and the flu are two completely separate viruses, both are set to circulate in tandem this fall, creating a perfect storm of illness, especially for more vulnerable populations like pregnant women.

“If someone were to come down with both COVID-19 and influenza at the same time, that would make fighting both infections harder on their body. While there’s not yet a vaccine for COVID, there is one for both the flu and H1N1, which can help prevent a scenario like that,” says Langdon.

What This Means for You

If you’re pregnant or considering adding a baby to your family this year, the best time to get a flu shot (which includes the more specific H1N1 flu shot) is now. It’s been determined to be a safe, effective way to stay healthier during the COVID-19 pandemic.

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Article Sources
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  1. Ludvigsson JF, Winell H, Sandin S, Cnattingius S, Stephansson O, Pasternak B. Maternal Influenza A(H1N1) Immunization During Pregnancy and Risk for Autism Spectrum Disorder in Offspring : A Cohort Study. Ann Intern Med. 2020. doi:10.7326/M20-0167

  2. Memoli MJ, Harvey H, Morens DM, Taubenberger JK. Influenza in pregnancy. Influenza Other Respir Viruses. 2013;7(6):1033-9. doi:10.1111/irv.12055

  3. Centers for Disease Control and Prevention. Vaccinating Pregnant Women. Updated October 8, 2019.

  4. Godlee F, Smith J, Marcovitch H. Wakefield’s article linking MMR vaccine and autism was fraudulentBMJ. 2011;342:c7452. doi:10.1136/bmj.c7452

  5. Centers for Disease Control and Prevention. 2009 H1N1 Pandemic (H1N1pdm09 virus). Updated June 11, 2019.

  6. Centers for Disease Control and Prevention. Who Needs a Flu Vaccine and When. Updated August 20, 2020.

  7. Centers for Disease Control and Prevention. Vaccination Guidance During a Pandemic. Updated June 9, 2020.