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Studies Confirm COVID-19 mRNA Vaccines Safe, Effective for Pregnant Women

Posted on by Dr. Francis Collins

Credit: GettyImages/bogdankosanovic

Clinical trials have shown that COVID-19 vaccines are remarkably effective in protecting those age 12 and up against infection by the coronavirus SARS-CoV-2. The expectation was that they would work just as well to protect pregnant women. But because pregnant women were excluded from the initial clinical trials, hard data on their safety and efficacy in this important group has been limited.

So, I’m pleased to report results from two new studies showing that the two COVID-19 mRNA vaccines now available in the United States appear to be completely safe for pregnant women. The women had good responses to the vaccines, producing needed levels of neutralizing antibodies and immune cells known as memory T cells, which may offer more lasting protection. The research also indicates that the vaccines might offer protection to infants born to vaccinated mothers.

In one study, published in JAMA [1], an NIH-supported team led by Dan Barouch, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, wanted to learn whether vaccines would protect mother and baby. To find out, they enrolled 103 women, aged 18 to 45, who chose to get either the Pfizer/BioNTech or Moderna mRNA vaccines from December 2020 through March 2021.

The sample included 30 pregnant women,16 women who were breastfeeding, and 57 women who were neither pregnant nor breastfeeding. Pregnant women in the study got their first dose of vaccine during any trimester, although most got their shots in the second or third trimester. Overall, the vaccine was well tolerated, although some women in each group developed a transient fever after the second vaccine dose, a common side effect in all groups that have been studied.

After vaccination, women in all groups produced antibodies against SARS-CoV-2. Importantly, those antibodies neutralized SARS-CoV-2 variants of concern. The researchers also found those antibodies in infant cord blood and breast milk, suggesting that they were passed on to afford some protection to infants early in life.

The other NIH-supported study, published in the journal Obstetrics & Gynecology, was conducted by a team led by Jeffery Goldstein, Northwestern’s Feinberg School of Medicine, Chicago [2]. To explore any possible safety concerns for pregnant women, the team took a first look for any negative effects of vaccination on the placenta, the vital organ that sustains the fetus during gestation.

The researchers detected no signs that the vaccines led to any unexpected damage to the placenta in this study, which included 84 women who received COVID-19 mRNA vaccines during pregnancy, most in the third trimester. As in the other study, the team found that vaccinated pregnant women showed a robust response to the vaccine, producing needed levels of neutralizing antibodies.

Overall, both studies show that COVID-19 mRNA vaccines are safe and effective in pregnancy, with the potential to benefit both mother and baby. Pregnant women also are more likely than women who aren’t pregnant to become severely ill should they become infected with this devastating coronavirus [3]. While pregnant women are urged to consult with their obstetrician about vaccination, growing evidence suggests that the best way for women during pregnancy or while breastfeeding to protect themselves and their families against COVID-19 is to roll up their sleeves and get either one of the mRNA vaccines now authorized for emergency use.


[1] Immunogenicity of COVID-19 mRNA vaccines in pregnant and lactating women. Collier AY, McMahan K, Yu J, Tostanoski LH, Aguayo R, Ansel J, Chandrashekar A, Patel S, Apraku Bondzie E, Sellers D, Barrett J, Sanborn O, Wan H, Chang A, Anioke T, Nkolola J, Bradshaw C, Jacob-Dolan C, Feldman J, Gebre M, Borducchi EN, Liu J, Schmidt AG, Suscovich T, Linde C, Alter G, Hacker MR, Barouch DH. JAMA. 2021 May 13.

[2] Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination in pregnancy: Measures of immunity and placental histopathology. Shanes ED, Otero S, Mithal LB, Mupanomunda CA, Miller ES, Goldstein JA. Obstet Gynecol. 2021 May 11.

[3] COVID-19 vaccines while pregnant or breastfeeding. Centers for Disease Control and Prevention.


COVID-19 Research (NIH)

Barouch Laboratory (Beth Israel Deaconess Medical Center and Harvard Medical School, Boston)

Jeffery Goldstein (Northwestern University Feinberg School of Medicine, Chicago)

NIH Support: National Institute of Allergy and Infectious Diseases; National Cancer Institute, National Institute of Child Health and Human Development; National Center for Advancing Translational Sciences; National Institute of Biomedical Imaging and Bioengineering


  • Tana Kalnbach says:

    How could they know that? There haven’t been any long-term studies and VAERS is backlogged with reports of adverse reactions. Slow down and focus on the elderly in our country and other countries.

    • Tana Kalnbach says:

      Yes, effective in 12 year olds and older but myocarditis and pericarditis are being investigated currently with this age group. Statistically zero hospitalization and fatality rate for this age group. Risk-Benefit?

    • Marin says:

      I’m an elderly person. Was vaccinated two months ago. My doctor ordered many routine blood test last week for my autoimmune conditions, including an antibody test, to see if I got enough protection and I don’t have any changes. No side effects. Feel great.

    • MICHELLE MUNIZ says:

      I agree! They should end public phase III trials, wait and sit back and really analyze the saers data and wait for the many independent studies to finalize..
      Covid curve is down and this is pretty much aftermath. To many professionals warning against theae injections and we don’t know any real life long term effects either.

    • Cale says:

      Go read the study. It explained how that came to believe this.

    • DeeniBeeni says:

      Agree 100%. They indicate it’s safe for the mother because there was “no damage to the placenta”, but how can they possibly know what the long-term effects will be on either the mother or the baby???

      As for the article’s author, ” appear to be completely safe for pregnant women” – remind yourself to do that statistics refresher course.

  • Shukri abdisalam says:

    Good news

  • Steve White says:

    As a layman American I want to thank everyone for all they did to fight the epidemic, BUT, I have to think – realizing hindsight is 20/20, but still – IF we had, after the first mRNA vaccines were prepared, given the makers of them a green light to vaccinate people at high risk of severe Covid, or if they were unwilling, FORCED them to make the vaccines in large quantities, to be bought by the government, then administered to high risk people on a voluntary basis, we might have kept serious illness way down.
    If this had been started in March and April, when the first testing of the two mRNA vaccines we are using now began, how many people could have been vaccinated before the midsummer surge, let alone the holiday peaks in states previously not much effected?
    I am going to say something I know will offend many medical people – I do not feel we learned from this epidemic – not very much – if we had another epidemic, and a vaccine was developed quickly, I believe it would be withheld, for, operationally, about a year, while the epidemic destroyed the country. The reasons given for withholding the vaccine will be, essentially, we’ve always done it this way and we can’t change that just because we have a once in a century pandemic.
    In the circumstances we faced – not solely the virus, which was very bad, but ultimately, shown to be mostly a threat to old folks, – but the REACTION to the virus, which was extremely destructive, generally – EVERY possible strategy should have been on the table. I see a massive failure I am very angry about, but worse, I think our enemies have seen the failures, and now know one more epidemic like this will destroy the US. We need to have a better plan for a future epidemic and I see no sign we will.

  • Eileen says:

    These studies do not address safety, they address effectiveness in pregnant and breast feeding women. The study from Chicago looked at placentas and at antibody levels. The authors assume the lack of placental abnormalities equals safety in the 33 (30% of the 80 enrolled) women whose placentas were examined. The study suffers from being underpowered and the populations were not controlled for. The JAMA paper enrolled a total of 103 women, 30 were vaccinated while pregnant. The results were entirely on immunogenicity with only a mention of “no severe adverse events or pregnancy or neonatal complications were observed.” An n of 30 is not an adequate study to infer anything. This study is way underpowered as well and too small to find any majority much less uncommon adverse events.
    For those who like to say they follow the science you need to read the papers Blogs like this one reference. There is virtually no meaningful safety data in either of these studies, despite what the blog states. Both studies do, however, give us effectiveness data.

    • Lindsey says:

      Thank you for your call out on the lack of clarity on this study. I am a woman of child bearing age with uncertainty if I will choose to have another child or not. At this point, I want the raw data from the studies – vaccination prior to pregnancy and during and the outcomes of the vaccinated individuals and their offspring. Not the findings of the data as they’ve been extrapolated by an individual or a group of medical professionals with good intentions but an unconscious bias. I asked my OB for a place where I could start to collect the data as it comes in (given the fact that we are just beginning to see women who may have received the vaccine prior to pregnancy and the outcomes of the pregnancy) and she could not point me to any single data source. She could only “reassure” me that ACOG promotes the vaccine. Again, I don’t need an endorsement by well intended medical professionals. I need the data so I can make an informed, educated decision on my own.

    • thedudern says:

      What are your qualifications to evaluate this study?

      • Yonason says:

        She sounds pretty knowledgeable to me, but…

        If you think she’s wrong, you should have no trouble pointing out why from the papers themselves, rather than questioning her qualifications, a far weaker argument.

  • Suzanne says:

    There are many, many more pregnant women who have taken the vaccine without being part of a research study. Myself included. If just one had adverse effects so far, it would have made international news. Even if it wasn’t caused by the vaccine.
    Pregnant women are at increased risk of hospitalization/death from the virus and the general public is at risk of the formation of vaccine-resistant variants popping up due to unvaccinated people.
    It was a great relief to me to know I wouldn’t play a part in anyone else getting sick. And that my healthy and happy newborn is likely to have immunity. When the vaccines are approved for younger children, I will happily have my 3-1/2 year-old vaccinated!

    • Erin M says:

      “If just one had adverse effects so far, it would have made international news. Even if it wasn’t caused by the vaccine.” Are you sure about that…. since our news sources are so clearly biased in encouraging ‘the jab’. It must be easy for others to say “pregnant women should get the vaccine” when they are in fact not pregnant and faced with that difficult decision. There are soo many things pregnant women should not consume or inject in their bodies while pregnant, but others are quick to say a 1 year old vaccine that nobody really knows the long term effects of, is okay for pregnant women. 1 year ago did they predict a booster shot would be needed? No. I rest my case.

  • Ranjith says:

    When gets the vaccine to the public?

  • Mike Anderson says:

    Thank you very much for this very important post.

  • Joan Da costa says:

    The value of trust in research studies and their publication. And summary write ups….is vitally important.
    When a write up over simplifies. Or let’s a casual reader draw am incorrect safety if efficacy conclusion. Beware. As trust. Is vital if this part of our county and world culture wants an vital and happily invited family member at our future crisis and holiday and every dinner table.
    Break trust. And the family member will be sat in the corner with the face to the wall.
    Trust and good data transparency and clear not deceptive summaries are vital.
    The choice to keep this family member at our dinner table. Or not. Is being asked by too many who see to many reasons not to trust.
    I think it is a vital member. But like a five year old. Needs to know the value of truth.

  • Lerrin Derooy says:

    Spanish flu was a vaccine
    60,000,000 dead.

  • Bryan says:

    The first study only looked at antibody response, it was not a safety study. Why are you even mentioning it here? The second study only ensured that the vaccine didn’t cause an immune response to the placenta? That is important, but by itself is a very weak and limited outcome measure. They did not even follow through to see if there was any injury to the newborns. And really, it will take a few years before more subtle neurological damage would even be noticeable. And the sample size is tiny.

    These are the studies on which the NIH is basing the claim that the vaccine does not cause reproductive harm? This is shocking and disgraceful. We need accountability.

  • DL says:

    We should just wait then, until we absolutely KNOW that everyone is SAFE from the vaccine. We can do a longitudinal study of say, 25 years? At that point, many of the infants exposed to the vaccine will be adults and you’ll have you definitive data. If everything looks good at that point, then you can get the vaccine for a virus that is 25 years old and likely doesn’t even resemble the original virus that caused the disease in the first place. Leave the vaccine out of it entirely until we KNOW for CERTAIN beyond ALL doubt that this thing is safe and take your chances on contracting the disease itself. I am glad my parents didn’t wait for the longitudinal Polio study to conclude, but, that being said, this sounds like a solid risk assessment strategy to me.

  • Danny says:

    These studies are weak. Far too small and have not looked at the babies. If this is what we are basing the “safe and effective” mantra on then we are truly lost. Amazing double standard when compared with the kind of evidence they are demanding for early treatments such as ivermectin or fluvoxamine. Hard not to be a conspiracy theorist.

  • Barbi says:

    n June 25, the FDA added new warnings for both vaccine provider and recipients to their fact sheets on Pfizer and Moderna over rare cases of heart inflammation called myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the lining outside the heart). The agency added the warnings just two days after the CDC’s Advisory Committee on Immunization Practices (ACIP) met and confirmed the “likely association” between myocarditis and pericarditis and the Pfizer and Moderna vaccines, both of which use mRNA. However, it’s rare, treatable, and usually mild, they say.

  • Jenny Jenkins says:

    Looks like some very helpful information! I read the entire article, and I love the writing style and passion in your posts . . .

  • Deanna says:

    I received the first dose of fed Pfizer vaccine when I was only a few weeks pregnant. (I didn’t know that I was pregnant at the time.) I received the second dose the end of January. I carried my baby to term, and I’m happy to say I have a very healthy, happy baby!! I had zero complications during pregnancy and in labor.

  • santhathi says:

    Thank you for sharing such an informative blog with us. I found this very useful for everyone . . .

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