Vaccines in Pregnancy (and Beyond)

"Remember, our job is not to force you to do anything you aren’t comfortable with. Our job is to help you understand the truth about risks and benefits of things that seem scary and unknown."

By Dr. Elizabeth Oler

The flu season is in full swing, and especially this year, there is reason to be extra vigilant about not getting sick. The good news is, you can protect yourself from potentially devastating consequences of certain infections, and even protect your baby, by getting known safe vaccines during your pregnancy.


Every single moment of your pregnancy, you are making what feels like life-or-death decisions. There is so much uncertainty and every choice can be scary! As your doctors and midwives, we are here to guide you to the right decisions as a team. Ultimately, our number one priority is the health and safety of you and baby, and we only recommend things that help us to reach that goal.


Before we launch into this, it’s important to know that not all vaccines are safe in pregnancy. For example, the MMR (measles, mumps, and rubella) is a live vaccine. Theoretically, live virus particles could cross the placenta and infect the baby, so we don’t risk it. On the flip side, there are several vaccines that we have proven over many years to be safe in pregnancy.


Let’s start with the Tdap vaccine. Tdap is recommended for all pregnant women at 28 weeks, because it protects the baby against pertussis, or whooping cough, through “passive immunity.” When you are vaccinated (or when you get sick), your immune system creates proteins called antibodies. Fortunately for your baby, passive immunity means that these antibodies cross the placenta, go into the baby’s bloodstream, and protect him or her after birth. If you’ve gotten the Tdap before, this is just a booster, so your body pumps out a lot more of those antibodies to give your baby adequate protection.


Why not let your baby get exposed naturally and create those antibodies themselves? Unfortunately, newborns don’t have a mature immune system, so they are more susceptible to getting sick until their bodies learn how to respond. Pertussis is a particularly bad one and can be really devastating in young babies. That’s why your antibodies are so important! And making this vaccine a routine part of pregnancy works – pertussis has become much rarer because of that Tdap shot in the third trimester.


Now, let’s talk about the flu shot, which is also safe in pregnancy. As many benefits as the flu shot has, there are as many, if not more, misconceptions about risks. If you feel anxious about it, you’re not alone! Below, I’ve put together a few common concerns I hear every day about why patients are holding back. Sadly, most of these fears are based on misinformation spread through the internet and social media. As someone who’s spent a lot of time and energy learning about vaccines in nitty gritty detail, I hope to reframe things in a way that both dispels the myths and eases your worries.

  1. “The flu shot gives me the flu every time I get it! I don’t want to get sick.”

Yes, it is true that the flu shot can give some people a mild inflammatory reaction. This is actually a “healthy” activation of your immune response. It is not the flu, because the vaccine does not contain any live virus. That little bit of inflammation is safe, and certainly better than the flu itself. Even better, we’ve found in population-scale studies that people who get the flu shot and then get the flu are less likely to have severe infection than those who don’t get vaccinated. It’s a win-win!

2. “I don’t want to get the flu shot because I have never gotten it, and I’ve never gotten sick.”

If you haven’t gotten sick from the flu in the past, lucky you! The flu can be deadly, and one of the reasons to get the flu shot is because it doesn’t just protect you – it protects everyone around you too. Furthermore, when you’re pregnant, your body is unfortunately working against you in ways that can make you sicker. Firstly, your immune system is weaker, which makes you more susceptible. Secondly, the strength and capacity of your lungs is diminished, so pregnant women are more likely to end up in an ICU on a ventilator from the flu than someone the same age who isn’t pregnant. If you wind up getting really sick, there is a good chance your baby would need to be delivered early to save your life, putting both of you at risk for bad outcomes.


3. “I don’t want the flu shot because I worry about the preservatives, and I don’t think they are natural or safe for me and my baby.”

The standard flu shot contains a small amount of thimerosal, which is a preservative that kills dangerous pathogens that could contaminate the vaccine vial. Without it, the vaccine would be much riskier. Thimerosal has a tiny amount of mercury, which makes people nervous. The good news is, this version of mercury, ethylmercury, is safer than the mercury that comes from the actual metal, called methylmercury, because ethylmercury is rapidly removed from your system. Some foods we eat have higher levels of mercury than the flu shot, and the amount in the shot is so negligible that over and over again, it’s been found in our studies to be completely safe. The risk of the flu is, again, so much higher!


4. “I got the flu shot in the past, and then I got the flu anyway, so I know it won’t work for me anyway. I’d rather just get the real flu!”

As we touched on in question 2, there are potentially devastating consequences of getting the flu when you’re pregnant. And again, although you can get the flu after the flu shot, it’s statistically less severe than it would have been without the vaccine. Even more concerning, large scientific studies suggest that there may be long-lasting effects of being sick during pregnancy. We still have a lot to learn here, but we are starting to believe that your baby’s brain development could be affected in subtle ways by infections. For example, there were higher rates of schizophrenia in people who were born during the 1918 flu pandemic. Although causation hasn’t been (and could never be) confirmed, we certainly know that the vaccine itself hasn’t been associated with any negative outcomes for moms or babies. So when calculating the risk to the pregnancy, it is important to keep this in mind!


5. “The flu isn’t that big of a deal anyway. It’s just a bad cold, and I’m otherwise healthy, so why put myself through an unnecessary shot?”

Hopefully all of the things I’ve said above have helped you realize that this just isn’t true. I’d like to reiterate here that the flu shot doesn’t just protect you – it protects everyone around you, too. As we’ve learned with COVID, the highest risk for spread is actually the people that don’t get very sick! You can do your part to keep yourself, your family, your baby, and your community healthier by getting vaccinated. It’s a small, incredibly safe, low risk act, with potentially huge benefits.


Now – if after all this – you still don’t want to get the flu shot, that is still ok! We hope that you at least convince everyone in your family and your close contacts to get vaccinated, so you can be protected by association, because that is powerful as well. Remember, our job is not to force you to do anything you aren’t comfortable with. Our job is to help you understand the truth about risks and benefits of things that seem scary and unknown. As you’ve probably already learned the hard way, people will constantly try to tell you what is best for you during your pregnancy, even when they aren’t asked or don’t know the facts. Not all information is created equal – so it is critical to choose your sources carefully when doing your research!


And remember once again that we are here to help you, protect you, and make this pregnancy as safe and successful as we can. Please feel free to ask us more at your prenatal visits – we want to help you make these decisions together as a team. It is our calling and our passion, and we are devoted to the best outcomes possible. We will support you no matter what you choose!