September 30, 2019
5 min read

‘Explain the science’: PCPs can improve flu vaccine uptake among pregnant women

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Jen Caudle
Jennifer Caudle

Pregnant women are “considered the most important risk group” that needs to get the influenza vaccine, researchers wrote in Vaccine. The CDC reported that pregnant women who are vaccinated lower their risk for influenza-related hospitalization by an average of 40%.

Yet, study findings show that most pregnant women aged 18 to 44 years did not get vaccinated during influenza seasons from 2012 to 2015.

“Pregnant women — due to changes in their heart, lungs and immune system — are especially at higher risk for getting more severe illness from the flu,” Jennifer Caudle, DO, associate professor of family medicine at Rowan University School of Osteopathic Medicine in New Jersey, said in an interview. “It is important for pregnant women to get the flu shot to not only protect themselves, but to protect their unborn baby as well,”.

Healio Primary Care spoke with Caudle about the evidence supporting influenza vaccination during pregnancy and the tools primary care physicians can use to help improve influenza vaccine uptake among this vulnerable population.

Image of a girl getting a vaccine.  
The CDC reported that pregnant women who are vaccinated lower their risk for influenza-related hospitalization by an average of 40%. Yet, study findings show that most pregnant women aged 18 to 44 years did not get vaccinated during influenza seasons from 2012 to 2015.


Evidence that influenza vaccines are safe

There is substantial evidence supporting the safety of influenza vaccination during pregnancy. Approximately 2 million pregnant women were immunized during influenza seasons between 2000 and 2003, and very few adverse events — most of them being injection-site reactions, fever, headache and myalgia — were reported to the United States’ Vaccine Adverse Event Reporting System, researchers wrote in Human Vaccine and Immunotherapeutics.

A more recent American College of Obstetrics and Gynecologist’s Committee Opinion titled “Influenza Vaccination During Pregnancy” also supports influenza immunizations for pregnant women.

“Numerous studies, including clinical trials and observational studies, and data from safety reporting systems have demonstrated consistently the safety of influenza vaccination during pregnancy,” the committee wrote in 2018.

One study that suggested that the influenza vaccine increased the likelihood for spontaneous abortion had research design flaws and its results have never been replicated, according to the ACOG.

Caudle provided insight on the vaccine’s impact on offspring.

“Unborn children whose mothers do not get the flu shot are at greater at risk for respiratory illnesses during their first few months of life, being born prematurely, and/or having a low birth weight, she said.

In fact, study findings published this year in Birth Defects Research demonstrated that severe influenza infection during pregnancy was associated with adverse outcomes among infants.

“Patients may express concerns that vaccines cause autism or increased risk for congenital malformations and/or fetal death,” she said in the interview. “Although as clinicians, most of us know that these are myths, it is possible that some women do not. In the case of a patient who has concerns about this, be prepared to discuss in laymen’s terms explain the science that debunks the myths.”

Recent studies have also shown that pregnant women who get vaccinated against influenza are also protecting their child during its first 6 months of life, according to Caudle.

“This is important, because there are currently no FDA-approved [influenza] vaccines for children who are less than 6 months old,” she explained.

In addition, infants who develop pertussis are at increased risk for hospitalization for death if their mother did not get an influenza vaccine, according to the authors of a PLoS Currents article.

“Patients should be told that that they are largely helping, not hurting, themselves and their baby when they get a flu shot. When it’s put in that context, I hope a patient would be much more likely to get one,” Caudle added.

Not all vaccines are appropriate

ACOG and the CDC indicate that any “licensed, recommended, and age-appropriate” recombinant influenza vaccine or inactivated influenza vaccine can be administered to pregnant women. Live-attenuated influenza vaccine should not be used during pregnancy.

ACOG adds that patients with a history of egg allergy who have experienced hives after exposure to egg can receive any licensed and recommended influenza vaccine “that is otherwise appropriate for their age and health status.”

Caudle discussed other cohorts of pregnant women that should not get an influenza vaccine.

Women with severe, life-threatening allergies to influenza vaccine or any ingredient in the vaccine, should not get the flu shot and should speak with their doctor about this,” she said.

But for most patients, these conditions do not apply.

“It’s also common for patients to think they will get the flu from a flu shot, but the evidence shows that is simply not true,” Caudle said.

Timing of influenza vaccination

A systematic review and meta-analysis published in Influenza and Other Respiratory Viruses provide some insight into the timing of the vaccination’s impact.

“Vaccinating a woman in early pregnancy will provide protection against influenza for a greater proportion of pregnancy but may increase the probability that this immunity will not last until delivery,” the authors concluded.


Caudle recommended that pregnant women get the influenza vaccine before the end of October but as soon as early as possible during flu season.

The CDC’s Advisory Committee on Immunization Practices and ACOG recommend that women who are or will be pregnant during influenza season should be administered “an inactivated influenza vaccine as soon as it is available” and that “vaccination throughout the influenza season is encouraged to ensure protection during the period of circulation.”

Exposure to influenza

ACOG states that regardless of a pregnant woman’s vaccination status, if she was exposed to someone else with influenza, she should take 75 mg of post-exposure antiviral chemoprophylaxis (Tamiflu [oseltamivir, Roche]), which should be administered once daily for 10 days. If oseltamivir is unavailable, Relenza (zanamivir, GlaxoSmithKline) can be substituted (two inhalations of 5 mg each, once daily for 10 days). – by Janel Miller


ACOG. Committee opinion on influenza vaccination during pregnancy. Accessed Sept. 6, 2019.

CDC. Flu vaccine and people with egg allergies. Accessed Sept. 8, 2019.

CDC. Guillain-Barré Syndrome. Accessed Sept. 9, 2019.

CDC. Pregnant Women & Influenza (Flu). Accessed Sept. 8, 2019.

CDC. Who Should and Who Should NOT get a Flu Vaccine. Accessed September 8, 2019.

Chamberlain, AT, et al. PLoS Curr. 2015;doi: 10.1371/currents.outbreaks.d37b61bceebae5a7a06d40a301cfa819.

Cuningham W, et al. Influenz Other Respir Viruses. 2019;doi:10.10.1111/irv.12649.

Ding H, et al. Am J Prev Med. 2019;doi:10.1016/j.amepre.2018.11.020.

Grohskopf LA, et al. MMWR Recomm Rep. 2019;doi:10.15585/mmwr.rr.6803a1.

McMillan M, et al. Vaccine. 2015;doi:10.1016/j.vaccine.2015.02.06.

Nunes MC, Madhi SA. F1000Res. 2018;doi:10.12688/f1000research.12473.1.

Sakala IG, et al. Hum Vaccin Immunother. 2016;doi:10.1080/21645515.2016.1215392.

Disclosure: Caudle reports no relevant financial disclosures.