Tdap Vaccine And Flu Shot In Pregnancy – What Your Doctor May Not Tell You


I guess I should start this post with a disclaimer for the FDA, CDC, ACIP, ACNM, ACOG, ABOG, the small green Martians and all the people out there I occasionally or regularly butt heads with, so here goes:

Disclaimer: I don’t believe everything I see. Neither do I believe everything I hear. You shouldn’t either. Don’t believe me. Use this blog and anything you read on this blog as a reference for your own research if you wish. Or don’t. Either way, the information contained on this website is provided for informational purposes only and does not constitute medical advice.

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It’s not that long ago when virtually all pregnant women were advised to stay away from all vaccines.

But, times have changed.

There are two vaccines currently recommended for most pregnant women:

  • Flu (influenza) shot
  • Tdap vaccine

Both vaccines are considered safe and effective.

Which means that extensive clinical trials have been done and these vaccines are unequivocally safe in pregnancy, right?

About that…

Shockingly, very little research has been available on the safety of maternal vaccines for both the mother and the developing fetus.

First, let’s talk about the flu shot in pregnancy.

Pregnant women can get the flu shot at any point in any trimester of their pregnancy.

Flu shot in pregnancy: Why is it recommended?

CDC: “Flu is more likely to cause severe illness in pregnant women than in healthy women who are not pregnant. In addition, studies have shown that vaccinating a pregnant woman also can protect a baby after birth from flu.”

You’re more than likely familiar with what the flu is, but if you’re not: it’s similar to cold except worse and more likely to cause complications.

Flu shot in pregnancy: Is it safe?

CDC: “Yes. Flu shots have been given to millions of pregnant women over many years with a good safety record. There is a large body of scientific studies that supports the safety of flu vaccine in pregnant women and their babies. CDC continues to gather data on this topic.” (And:) “There is a lot of evidence that flu vaccines can be given safely during pregnancy, though these data are limited for the first trimester.“


What exactly is the large body of scientific studies the CDC is referring to?

(1) Review of reports to the Vaccine Adverse Reporting System (VAERS) (Moro et al, 2011, Moro et al, 2011, Moro et al, 2017) found no evidence to suggest a link between pregnancy complications or adverse fetal outcomes among pregnant women and flu shots.


If you’re not familiar with what VAERS is, it’s a passive reporting system intended to monitor post-licensure vaccine safety. Reports can be submitted by virtually anyone: healthcare providers, patients, or family members. The problem with VAERS is that negative outcomes tend to be grossly underreported (the exact level of underreporting isn’t known).

CDC admits that: “Passive surveillance systems (e.g., VAERS) are subject to multiple limitations, including underreporting, reporting of temporal associations or unconfirmed diagnoses, and lack of denominator data and unbiased comparison groups.”

But they also state the following: “Because of these limitations, determining causal associations between vaccines and adverse events from VAERS reports is usually not possible.” Clearly, a link cannot be established regardless of what VAERS data the CDC works with. (Source of citations: CDC.)

(2) A study using 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.

The data provided by Vaccine Safety Datalink (VSD) are from before 2009 when the H1N1 strain was added to the mix.

Since then, a study found that women vaccinated early in pregnancy with a flu vaccine containing the pandemic H1N1 (H1N1pdm09) component who had also been vaccinated the prior season with an H1N1pdm09-containing flu vaccine had an increased risk of spontaneous abortion (miscarriage) in the 28 days after vaccination between the years 2010 and 2012. Most miscarriages occurred in the first trimester, several occurred in the second trimester. The study did not establish a casual relationship between repeated influenza vaccinations and miscarriage but suggested that further research was warranted.

CDC states that there IS an ongoing investigation to study this issue further among women who were pregnant and eligible to receive flu vaccine during the 2012-13 through 2014-15 flu seasons. Results are anticipated in late 2018 or 2019. (Source: CDC.) (Guess who the unknowingly enrolled study subjects are? You betcha. The pregnant women that were vaccinated between 2012 – 2015 that were undeniably told by their doctors that the flu vaccine was safe.)

It could be that the issue was certain batches of flu vaccines used between 2010 – 2012, it could mean that any two consecutive annual flu shots containing the H1N1 strain could be the problem in some pregnant women, or it could be something else. We don’t know.

(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.

Besides the fact that flu shots given prior to late 2009 were different from those given from late 2009 onward, this study observed pregnant women for 42 days only, and only a few conditions were looked at: hyperemesis (severe nausea), chronic hypertension, gestational hypertension, gestational diabetes, proteinuria, urinary tract infection, preeclampsia or eclampsia, chorioamnionitis (intra-amniotic infection), puerperal infection, venous complications, pulmonary embolism, and peripartum cardiomyopathy. Fetal or maternal death, hospitalizations, or spontaneous abortions were not included in this study.

(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. The study found no differences between the two groups in the rates of premature delivery or small for gestational age infants.

Here we go again using data related to vaccines that are no longer used. Also, the focus of the study were only rates of premature delivery and small for gestational age births.


(5) A large August 2017 study using VSD data found that the babies of women who received the flu shot during their first trimester had no increased risk of having children with major birth defects.

This study, limited to vaccine application in the first trimester (though, admittedly, this is a period of greatest fetal vulnerability), focused on selected major structural birth defects in full-term live births (cases of spontaneous abortions or maternal of fetal deaths were excluded from the study).

Flu shot in pregnancy: How effective is it?

When it comes to determining flu vaccine efficacy, it’s anyone’s guess, really. The composition of flu vaccines is reviewed annually, but no one really knows ahead of time how well the vaccine strains will match the actually circulating flu strains each and every year. Some years it’s better, other years it’s laughable.

Also, the jury is still out on the overall effectiveness of the flu shot, and many conflicts of interest in funding studies have been registered so far.

(For more information on flu vaccines, find the package inserts here, or go straight to Fluzone® Quadrivalent, Flulaval Quadrivalent, or Flucelvax Quadrivalent.)


What about Tdap in pregnancy?

CDC recommends that pregnant women receive the Tdap vaccine between 27 and 36 weeks of pregnancy, regardless of when they had the last Tdap shot.

Tdap vaccine in pregnancy: Why is it recommended?

Tdap is a combination vaccine of (1) tetanus toxoid, (2) diphtheria toxoid, and (3) acellular pertussis. The third compound – pertussis – is the reason this vaccine is given in pregnancy.

CDC: “In October 2012, the Advisory Committee on Immunization Practices (ACIP) voted to recommend that healthcare personnel should administer a dose of Tdap during each pregnancy irrespective of the patient’s prior history of receiving Tdap (or Td). This strategy not only helps protect the mother from getting and passing pertussis on to her infant, but also provides passive immunity to the infant.”

What is pertussis?

Also known as whooping cough, pertussis is a highly contagious respiratory disease, with infants being at greater risk of complications. Pertussis is known for uncontrollable violent coughing with the need to take deep breaths after cough fits, also referred to as a whooping sound (hence the name “whooping cough”).

Tdap vaccine in pregnancy: Is it safe?

That depends on who you ask. According to CDC, yes. The manufacturers are a bit more cautious though.

Currently, there are two Tdap vaccines approved for use in adolescents and adults:

  • BOOSTRIX is a Category B drug which means that no risks have been found in humans. A developmental toxicity study has been performed in female rats and revealed no evidence of harm to the fetus. However, there are no adequate and well-controlled studies in pregnant women.

Package insert: “Because animal reproduction studies are not always predictive of human response, Boostrix should be given to a pregnant woman only if clearly needed.”

  • ADACEL is a Category C drug which means that not enough research has been done to determine if it’s safe. No animal reproduction studies have been conducted, and it is not known whether Adacel vaccine can cause fetal harm when administered to a pregnant woman.

Package insert: “Adacel vaccine should be given to a pregnant woman only if clearly needed.”

How safe is “safe”???

Both Sanofi Pasteur (Adacel) and GlaxoSmithKline (Boostrix) created registries, collecting information from pregnant women that have received the vaccine. Neither manufacturer has reported any safety signals. (The CDC has not seen any reports.)

Several retrospective observational cohort studies have been completed to date, which means that some pregnant women were observed after being given a vaccine in pregnancy which has not been proven to be safe for them to receive in the first place, and they were compared short-term with those that hadn’t received the vaccine. Many of these studies excluded women with pregnancies resulting in non-live birth outcomes (spontaneous abortion, fetal or maternal death), or pointed out that findings may have been limited by incomplete data or bias.

Tdap vaccine in pregnancy – How effective is it?

The reason for maternal Tdap vaccine push is because – per CDC – postpartum Tdap administration of the vaccine isn’t optimal since it does not provide direct protection to the infant. Furthermore, it takes about 2 weeks for the mother to develop protective antibodies against pertussis should she choose to vaccinate herself postpartum, thus exposing her newborn to unnecessary risk if she contracts pertussis in the meantime. Also, the newborn is at risk of contracting pertussis from other family members and caregivers. (Source: CDC.)


In late 2013, the FDA issued the following statement:

“A new study is helping to provide a better understanding of vaccines for whooping cough, the common name for the disease pertussis. Based on an animal model, the study conducted by the U.S. Food and Drug Administration (FDA) and published November 25, 2013, in The Proceedings of the National Academy of Sciences, shows that acellular pertussis vaccines licensed by the FDA are effective in preventing the disease among those vaccinated, but suggests that they may not prevent infection from the bacteria that causes whooping cough in those vaccinated or its spread to other people, including those who may not be vaccinated.” — (FDA has since taken the statement down or moved it, but it can be found elsewhere, including here.)


The reality is, latest findings show that while the vaccine may protect vaccinated against severe symptoms if infected with pertussis (which esentially means reducing the severity of cough), the same vaccinated individuals may become asymptomatic carriers of the disease and spread it to other subjects, including those most vulnerable, such as infants. (Read the study here.)

Kind of a slippery slope to recommend the vaccine for those that will be in contact with an infant, isn’t it?


Tdap vaccine is designed to protect against B. pertussis, not B. parapertussis, which is just another strain capable of producing whooping cough.

Should YOU get vaccinated with the flu vaccine or Tdap this pregnancy?

That should be your informed decision.

Always read the package insert.

Part of making an informed decision includes reading the package insert of any vaccine you’re considering getting. (Find package inserts of vaccines here.)

Pregnant women should be especially vigilant about exposure to any chemicals that could potentially cause harm to the developing fetus, including substances that haven’t been properly tested.

Are you already immune?

If you want to know whether you have pertussis antibodies before getting the vaccine, ask your healthcare provider to order a titer test. (You may have to pay for the test out of pocket.)

If your body is providing protective antibodies, you’re going to pass those onto your baby without the vaccine, plus later on via breast milk (if breastfeeding).

Practice good hygiene!

Frequent hand washing is the most effective way to prevent the spread of communicable diseases. Using alcohol-based hand sanitizer also helps if it’s all you’re left with (ditch antibacterial products which promote the growth of superbugs).

Live healthy.

Eat a healthy balanced diet that includes adequate amounts of phytonutrients, vitamins, and minerals (lots of fruits and veggies – preferably in their raw state!), and don’t forget about quality probiotics! Make sure you get adequate sleep, and keep in mind that some exercise is better than no exercise.

Garlic and ginger are great immune boosters that are safe in pregnancy, and if you’re not scared by FDA’s finger pointing at the amazing elderberries, elderberry syrup works wonders, too.

Be cautious…

If you have any questions or concerns, don’t hesitate to talk to your doctor to address these.

Any pregnant woman with a high fever, vaginal bleeding, severe headache, or difficulty in breathing should call her healthcare provider immediately.

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Before I go, just so we’re clear – I’m not saying don’t do it, OK? I’m not saying don’t get vaccinated! I’m just sharing some of the facts that are out there that don’t get a lot of attention.


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