Effects of COVID Vaccine on Pregnancy and Nursing - Happy as a Mother

Effects of COVID Vaccine on Pregnancy and Nursing

with OB-GYN Dr. Marta Perez


  • How vaccines work
  • The vaccine was created so quickly. Has it been adequately researched?
  • COVID vaccines and pregnancy
  • COVID vaccines and nursing
  • Vaccines and developing babies
  • Vaccinating children
  • Additional considerations of the vaccine

Parenting during a pandemic has been so hard! And now a swiftly developed vaccine has been rolled out, and members of my community have expressed a lot of anxiety about how safe these new vaccines might be during pregnancy and nursing. Dr. Marta Perez is an OB-GYN and she’s agreed to explain to us the risks of the vaccine versus not being vaccinated for pregnant or nursing people.

How vaccines work

“Vaccines work by priming the immune system and teaching it how to respond,” Dr. Perez explained. There are lots of different vaccines. The new ones are MRNA vaccines. There are also adenovector vaccines and vaccines made out of viral particles referred to as “live” vaccines, because they may have live virus particles. The COVID vaccines aren’t live. We’re only dealing with MRNA and and adenovector vaccines, but they all work by training your immune system how to respond if it comes in contact with the virus. “However the vaccine works, it introduces these foreign particles into your body. Your body says, ‘What is this?’ and produces antibodies,” Dr. Perez told us. 

There is a lot of focus on antibodies right now, because they’re easy to check for. We can test and see if you have antibodies. You also have memory cells that hold onto that information for you, but it’s much harder to check for that kind of immunity. You can’t really test for it.

With the COVID vaccine, immunity from the vaccine is actually better than immunity from the virus. The vaccine is targeted. You can think of it as the vaccine targets the virus’s shield. But if you contract the virus, the whole virus is working through your body and your body’s just reacting to it. It’s not a targeted approach. “Another common myth is, ‘I had the virus. I don’t need the vaccine,” Dr. Perez said. But we’re seeing the immune response to the vaccine is stronger than the immune response to the virus. So the vaccine is still a good idea.

The vaccine was created so quickly. Has it been adequately researched?

MRNA vaccine (Pfizer and Moderna), Adenovector vaccine (Johnson & Johnson and Astrazeneca) 

“As far as the U.S., the vaccines underwent a completely normal application, testing, and review process before their emergency use authorizations which can happen as soon as 3 months,” Dr. Perez said. The vaccine was approved quickly, but nothing was skipped in the process. Instead of waiting between each step, they were able to move to the next step immediately for emergency use authorization. “At 6 months they will be approved for full use authorization, and we’ll watch that process unfold now too,” Dr. Perez explained. 

The MRNA vaccines came out first and there have been very few side effects. You see the expected effects of the vaccine with people not feeling very well, but that’s common. “Reports of serious adverse events have been really, really, really low,” Perez said. Johnson & Johnson is an adenovector vaccine and is also extremely safe. We had more people go through these trials than most vaccine trials which is part of the reason the studies went so fast. We had plenty of participants.

Dr. Perez mentioned she’s heard people worry about the effects of the vaccine over the long term, because the drugs are so new. But she’s quick to point out that the rare adverse effects of vaccines where someone’s immune system went into overdrive in response to the vaccine happens over weeks not months or years. Of all the vaccines we have, the data shows the serious side effects occurring in weeks after the vaccine. So, we don’t know how this vaccine is going to pan out over years, but we do know how vaccines in general work. It’s also important to note that any adverse reaction to vaccines would likely be worse if you contracted the virus.

“Scientists don’t expect there to be long term effects of the vaccines, because even in the beginning of vaccines, we didn’t see this,” Dr. Perez said. Vaccines don’t stay in our bodies long term, so it’s not like repeated exposure to a medication that’s ingested daily.

“There is absolutely no scientific or medical  impact on fertility from the vaccine,” Dr. Perez said. There was a meme going around for a while saying the vaccine might impact fertility or sperm count, but that was a misunderstanding of misinformation. There is no basis for that. 

COVID Vaccines And Pregnancy

Dr. Perez said, “The alternative to getting the vaccine is getting COVID-19 which we know has risks to pregnancy.” 

This is something that comes up a lot with anxiety and depression during pregnancy too. A lot of people will say pregnant people shouldn’t take antidepressants, because it’s bad for the developing baby when research shows the effects of depression and anxiety in utero are stronger and riskier than the medication. “Every person and their situation is unique,” Dr. Perez explained. One person may be able to not take medication and another person may need it. 

A pregnant person might have anxiety or depression around the vaccine, and that makes sense. Especially if you’ve been through a fertility journey, or maybe lost other pregnancies. You may be super protective of that little bean. “Making the decision that is right for you and understanding it’s a complicated decision is totally fine, and you may change your mind,” Dr. Perez told us. Something might happen to change your mind either way, so talk to some people—not everyone, because there’s a lot of misinformation out there—but talk to trusted sources and come to a decision you can handle.

“One vaccine is not better than another. None of the trials included pregnant people,” Dr. Perez said. We are getting some retrospective evidence from people who were treated retroactively and pregnant people are now being included in the trials. The data coming out shows pregnancy doesn’t change the effectiveness of the MRNA vaccines, and we’ve even seen antibodies passed through the umbilical cord and in breast milk, so there may be some immunity for the baby as well. 

And pregnancy hasn’t caused an increase in side effects for the MRNA drugs. The flu-like symptoms and sore arms are still common, but there was no increase in adverse reactions. There isn’t information on the Johnson & Johnson vaccines yet. “I wouldn’t expect an increase in adverse reactions, and I would expect it to still be effective,” Dr. Perez informed us. “But because we don’t know I can’t make a recommendation one way or the other.” 

But based on what we know about the effects of COVID on pregnancy any vaccine is probably better than none at all. “I would get the vaccine that is available.” she said. 

COVID Vaccines And Nursing

IGG is an antibody that takes longer for our bodies to produce, but it’s longer lasting “IGG crosses the placenta like crazy. As a pregnant person, you are constantly giving IGG to all the stuff you had in your life to the baby,” Dr. Perez said. “IGG is in breast milk, but we don’t know how much immunity it gives the baby. It could be that it just reaches the baby’s stomach and is broken down.” It could be helpful in a way we don’t know about, but what we know is that it matters during pregnancy.

“IGA is a type of antibody your body makes when you’ve had an infection in a mucous membrane,” Perez explained. This antibody has something to do with location. It’s developed where an infection has developed. Secretory IGA is the type of IGA found in breast milk and it’s probably responsible for the immunity benefits of breast milk. It coats the middle of the baby’s throat, and because babies are always spitting up, it probably coats their respiratory tracts as well.

“There is without a doubt immune benefits to breastfeeding, and there are other benefits to breastfeeding. But it’s not black and white,” she continued. When it comes to COVID, there is anti-spike IGG and anti-spike IGA in breast milk. But we don’t know how much immunity it provides, because we haven’t been testing infants.

As babies start eating more they get less breast milk, and toddlers don’t nurse. If they do nurse, it’s a small percentage of their calories. It’s not harmful to toddlers to breastfeed, but that small amount of breast milk might not matter much to them. We also don’t know if a toddler’s immune system responds to breast milk the same way a baby’s does because they’re starting to develop their own immunities. That’s not to discourage anyone, but we don’t want to encourage false hope either! But it is reassuring for people who are nursing and want to be vaccinated that the potential for passing immunity is there.

There is no research on how the vaccine may or may not affect milk supply, but Dr. Perez’s baby was exclusively breastfed and she got the vaccine.

Vaccines And Developing Babies

We don’t have much information on this yet, but one study did show that pregnancy complications among people who had received the vaccine weren’t higher than what you would expect to find in the general population. That’s good news. We’re seeing emerging reassuring evidence for pregnant people, this is the biggest question pregnant people have. 

Even from the beginning The Society for Maternal Fetal Medicine and American College of Obstetricians and Gynecologists said in terms of how vaccines would work, we don’t expect the vaccine to be risky. 

When pregnant people get the flu, they have a higher risk of complications and death. Pregnant people should always get the flu vaccine no matter what part of pregnancy you’re in. If you’re pregnant during flu season, it’s important to get the flu vaccine. 

Another vaccine recommended during pregnancy is the TDAP vaccine. TDAP is tetanus, diphtheria, pertussis, and it’s recommended for pregnant people because of the pertussis, commonly known as whooping cough, which for adults is an annoying cough or you may be asymptomatic. But in babies with developing lungs or newly developed lungs it’s life threatening. This is usually given to pregnant people during the third trimester, because that gives the baby the most immunity at birth. 

But right now COVID is the biggest danger to everyone. The pandemic is like COVID’s flu season, so right now that vaccine takes priority. “We recommend two weeks between vaccines, so if you need to take the TDAP vaccine a little earlier than twenty-eight weeks or a little later than twenty-eight weeks to get the COVID vaccine, that’s okay.

Vaccinating Children

Pfizer is doing studies with children as young as six months, and they had overwhelming responses for participation, so they’re not currently recruiting. This could become a part of childhood vaccination. It’s not possible to say right now what vaccination and the Coronavirus is going to play out. It could be like a flu shot where you get one every year, or it could be the kind of thing you get once and then get a booster as needed. With some vaccines, you only need a vaccine once every ten years.

Additional Considerations of the Vaccine

Some people are concerned about the use of fetal tissue in the vaccines. However, the fetal cell line used in vaccines is from the 70s, so it’s just a collection of cells at this point. Since it is a specific line of cells we know where it was used, and it wasn’t used in the Pfizer or Moderna vaccines. So, if this is a moral concern, the MRNA vaccines are safe.

There are so many levels of risks and considerations for each person to take into account. For someone on the front line every day, a vaccine might be the best choice, but for someone who can eliminate most risks and get the vaccine during nursing that might work out for you. This is just about giving you the information to make the best decision for your family.

COVID can be triggering. Hopefully this has given you enough information to reduce your anxiety, but there are more resources available for coping with COVID!

Marta Perez M.D. is a board-certified OB-GYN and Assistant Professor of Obstetrics & Gynecology at WashU School of Medicine in St. Louis where she works as a Laborist caring for hospitalized pregnant and postpartum patients. She has a passion for perinatal health communication, maternal health disparities, and expanding postpartum care. She is a new mom herself and when not at the hospital she enjoys cooking, running, and reading.





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