This post is current as of November 9, 2021, and will be updated as new data and recommendations are released.
In a testament to the marvels of modern science, one COVID-19 vaccine (Pfizer) has been approved by the FDA and two have been granted emergency use authorization (Moderna and Johnson & Johnson) in the year since the pandemic took hold across the globe. While these vaccines differ a bit in how they work, the important thing they have in common is that they’re extremely effective in preventing severe cases of COVID-19 (yes, even cases of COVID-19 caused by the delta variant!).
People who were pregnant or breastfeeding/chestfeeding were excluded from previous stages of clinical trials for the vaccines. But based on published findings on preliminary surveillance data from the Centers for Disease Control and Prevention (CDC) (along with findings from many other peer-reviewed articles), there's growing evidence that these vaccines are safe and effective for people who are trying to conceive, currently pregnant, or breastfeeding/chestfeeding.
Medical and public health organizations like the American College of Obstetricians and Gynecologists (ACOG), the American Society of Reproductive Medicine (ASRM), the CDC, and countless others have released statements recommending that all of these groups get the COVID-19 vaccine. Additionally, ACOG recommends that all fully vaccinated pregnant or recently pregnant people get the booster dose of the vaccine — and that anyone who’s at increased risk of exposure does the same.
In this post, we’ll review COVID-19 vaccine basics (including efficacy and side effects), what we know about the effects of the vaccine on future fertility and reproductive outcomes, and what the data tells us about vaccination in pregnant and breastfeeding/chestfeeding people.
COVID-19 vaccine + fertility: Main takeaways
- The CDC recommends COVID-19 vaccination for everyone who's eligible, "including people who are pregnant, breastfeeding, trying to get pregnant now, or might become pregnant in the future." ACOG and 20 other leading medical organizations "strongly urge" the same.
- ASRM recommends COVID-19 vaccination for all people "who are contemplating pregnancy or who are pregnant to minimize risks to themselves and their pregnancy."
- ACOG recommends that all fully vaccinated pregnant or recently pregnant people (up to six weeks postpartum) get the booster dose of the vaccine — and that anyone who's at increased risk of exposure get the booster at least 2-6 months (two months for Johnson & Johnson, six months for Moderna and Pfizer) after being fully vaccinated.
- The CDC also states, along with ASRM, that there's no evidence that COVID-19 vaccination will impact the fertility of people with ovaries or people with sperm. Studies (like here and here) back these statements up.
- People who were pregnant or breastfeeding/chestfeeding were excluded from the phase 3 trials evaluating COVID-19 vaccine efficacy, but published findings of large-scale data from 35,000+ vaccinated pregnant people found no safety concerns for the birthing parent or for the baby. Recent meta-analyses confirm this.
- In contrast, there’s growing evidence that COVID-19 itself has negative effects on maternal and neonatal outcomes.
- There's also growing evidence (here and here, and analyzed across several studies here) suggesting that pregnant and breastfeeding/chestfeeding people who get vaccinated pass the benefits of the vaccine (aka COVID-19-fighting antibodies) along to a baby via the placenta or breast/chest milk, potentially protecting these newborns and infants against COVID-19.
First up: What COVID-19 vaccines are FDA-approved for use in the US?
The Pfizer vaccine got the FDA stamp of approval on August 23, 2021. Both the Pfizer vaccine and the Modern vaccine (which is authorized for emergency use) are mRNA vaccines, while the Johnson & Johnson vaccine is an adenovirus-based vaccine. Adenovirus-based vaccines have been around for a long time, and though the Pfizer and Moderna vaccines are the first-ever FDA-authorized mRNA-based vaccines, research on mRNA-based vaccines started almost 30 years ago.
At their core, all the currently available vaccines work in very similar ways — and none of them use the live virus that causes COVID-19 (so if you get the vaccine, you aren’t getting COVID-19 injected into your body). And, though they provide your body with the DNA or mRNA to stimulate the creation of antibodies, these vaccines can’t change your own DNA.
Here’s a quick rundown on how the different COVID-19 vaccines work:
mRNA-vaccines (Pfizer and Moderna)
The COVID-19 virus is notable for the spikes on its exterior, which are really just proteins called S proteins. When your body detects these spikes or S proteins, it recognizes them as intruders and the immune system gets to work trying to eradicate them.
The COVID-19 mRNA vaccines provide our bodies with the template to create these S proteins. When the molecular template gets injected, the body uses it to produce the unique S proteins. Once they’re detected, the immune system creates antibodies to destroy these proteins (and thus, would destroy any viruses that have these proteins on them). Both vaccines require one initial dose and a second dose about three weeks later.
Adenovirus vaccines (Johnson & Johnson)
The Johnson & Johnson vaccine relies on the same underlying logic: inject the body with something that jumpstarts the creation of S proteins, and provoke the immune system to create antibodies to destroy these proteins and any virus that has them on the surface. The key difference is in how the different vaccines tell your body to produce the S proteins.
The Pfizer and Moderna vaccines deliver the message in the form of mRNA, while the Johnson & Johnson vaccine delivers the message in the form of DNA that is attached to a non-harmful, inactivated virus (the “adenovirus”). Because DNA breaks down more slowly than mRNA, the Johnson & Johnson vaccine can be stored at warmer temperatures — while the Pfizer vaccine has to be stored at temperatures below -76 degrees Fahrenheit (brrr), the Johnson & Johnson vaccine can be stored at normal refrigeration temperature (between 36 and 46 degrees Fahrenheit) for several months. Unlike the two-dose Pfizer and Moderna vaccines, the Johnson & Johnson vaccine requires a single dose.
While the CDC and FDA paused the distribution of the Johnson & Johnson vaccine on April 13, 2021 “out of an abundance of caution” to investigate a very small number of cases (six in 6.8 million doses) of a rare type of blood clot that were detected after vaccination, the pause was lifted on April 23, 2021. That said, ACOG advises that people with ovaries under the age of 50 should be made "aware of the rare risk of thrombosis with thrombocytopenia syndrome (TTS)" after getting the Johnson & Johnson vaccine.
On October 21, the CDC endorsed COVID-19 booster shots (which can be mixed and matched with the original vaccine received) for all eligible populations for additional protection from the virus. On November 3, ACOG recommended that all fully vaccinated pregnant or recently pregnant (up to six weeks postpartum) people get the booster dose. For anyone who's at increased risk of COVID-19 exposure and fully vaccinated, ACOG added that they should get the booster at least 2-6 months (two months for Johnson & Johnson, six months for Moderna and Pfizer).
What do we know about the efficacy, safety, and side effects of the COVID-19 vaccine?
All COVID-19 vaccines are pretty remarkable in terms of how well they protect against serious illness and death. They’re all 100% effective in protecting against death from COVID-19, and between 85% and 100% effective in preventing serious COVID-19 illness. While the delta variant is the most transmissible COVID-19 variant detected to date, vaccines are still very effective at preventing serious illness and death. Data from one July 2021 study pinned the Pfizer vaccine’s effectiveness of preventing symptomatic illness at 94% for the alpha variant, and 88% for the delta variant. To put it in perspective: The yearly flu shot is usually between 40% and 60% effective.
The safety and side effect profile of these vaccines is similar to that of other common vaccines. It’s not uncommon to experience pain at the injection site, fatigue, or headaches. Some people may also experience flu-like symptoms. None of these side effects are clinically concerning, but they should be addressed by a physician if they don’t go away within three days.
How do these known side effects compare to the potential side effects of the virus itself? Though roughly 30% of COVID-19 cases are asymptomatic (i.e., there are no noticeable symptoms), 70% of people will experience symptoms — and these symptoms are similar to or more severe than the known side effects of the vaccine. Pregnant people who get COVID-19 are roughly 5x more likely to have severe symptoms if they contract COVID-19 relative to non-pregnant people, meaning the benefits of vaccination may be particularly notable for pregnant people.
Other factors that may make vaccination even more important include:
- Living in an area with a higher level of community spread: Check out this resource from Johns Hopkins (which is updated daily) to get an idea of community spread in your county.
- Working in a job that puts you at higher risk of contracting COVID-19: For example, it is even more important for essential and frontline workers who may have to interact with people on a day-to-day basis to get vaccinated because they may be at higher risk of contracting COVID-19.
- Having certain health- or lifestyle-related factors that put you at greater risk for severe illness if you were to contract COVID-19: Research shows that people who have heart conditions, diabetes, a higher body-fat percentage, and who are immunocompromised may be at greater risk for severe symptoms of COVID-19.
Is the COVID-19 vaccine safe if you’re currently trying to get pregnant or want to have kids one day?
Studies have shown that the COVID-19 vaccine has no effect on outcomes during IVF, sperm parameters, or markers of ovarian function or oocyte quality in people undergoing IVF. Recent systematic reviews of the topic come to the same conclusion: While more data is always better, all signs we currently have point to the COVID-19 vaccines having no impact on fertility. And, as OB-GYN and Modern Fertility medical advisor Dr. Jane van Dis, MD, FACOG adds, "Thousands of people have become pregnant since getting the vaccine with no signals that there is any risk of infertility." Based on this info, as well as the science and mechanism of the vaccines, top clinical bodies have weighed in with their recommendations:
- On August 11, 2021, the CDC updated their guidelines, recommending that "all people 12 years and older, including people who are pregnant, breastfeeding, trying to get pregnant now, or might become pregnant in the future" get the COVID-19 vaccine. In their update, they also clarify that there's "no evidence that any vaccines, including COVID-19 vaccines, cause fertility problems in women or men."
- On August 9, 2021, over 20 of the country's leading organizations for maternal care (including ACOG and the Society for Maternal-Fetal Medicine) released a joint statement saying: "We strongly urge all pregnant individuals — along with recently pregnant, planning to become pregnant, lactating, and other eligible individuals — to be vaccinated against COVID-19." They also suggest that "those planning to become pregnant should feel confident in choosing vaccination to protect themselves, their infants, their families, and their communities.”
- In ASRM’s May 19, 2021 statement, they recommended COVID-19 vaccination for all people "who are contemplating pregnancy or who are pregnant to minimize risks to themselves and their pregnancy." In their July 23, 2021 statement, they added that "COVID-19 vaccination does not impact male or female fertility or fertility treatment outcomes.”
The idea that the COVID-19 vaccine could cause infertility in people with ovaries came from a now-debunked (by numerous experts) article. The article claimed that the vaccine would cause the body to attack a protein that’s crucial to the formation of the placenta (the organ that provides a fetus nutrients during pregnancy). Though this important placental protein and S protein produced by the COVID-19 vaccine have similar biological functions (they both cause membrane fusion), they are not related — nor are they structurally similar enough for a vaccine targeting one to affect the other. (Read reproductive endocrinologist Dr. Lora Shahine’s take on this for more info.)
If you're considering whether or not you want to start trying to conceive right now, we’ve created a guide detailing some factors you and your partner may want to consider. And speaking of your partner (if you have one): They should consider getting vaccinated too, even if they’re not the one trying to get pregnant. If someone trying to get pregnant decides not to get the COVID-19 vaccine, it may be all the more important for the people they spend time with to get vaccinated.
Dr. Sharon Briggs, PhD, head of clinical product and research here at Modern Fertility, adds that if you're currently thinking about getting pregnant and you're concerned about the fact that data on vaccinated pregnant people is still ongoing, "getting vaccinated before you start trying to conceive is a great option.”
Can the COVID-19 vaccine affect your period?
Most vaccine trials do not ask about temporary changes in menstrual cycles when asking participants to report on side effects. This means that we generally have very little understanding of if and how vaccines affect menstrual bleeding or timing. There are reasons to think there could be links here, as outlined by Dr. Jen Gunter. Any changes between menstrual cycle-related characteristics and the vaccine could be indirectly caused by the stress of getting vaccinated. Or these changes could be a direct effect of the immune system response that is initiated by vaccines on the uterine lining. Check out our deep dive on the potential links between the COVID-19 vaccine and menstrual cycles to learn more.
While people have relied on anecdotal reports of temporary changes in period-related characteristics post-vaccine, the first systematic data on these data have recently been posted online. A group of researchers at the University of Illinois ran an IRB-approved study of periods in people who menstruate who recently got vaxxed. In their pre-print (which is a scientific paper that hasn’t been peer-reviewed and published yet) based on data from over 39,000 *thousand* participants, they found that about 56% of regularly menstruating people reported some sort of change to their menstrual cycle after being vaccinated.
Importantly, the authors stress that these short-term changes are not unexpected, and do not impact fertility or reproductive function in the long run. Short-term changes in menstrual patterns can be seen as a result of things like psychological stress, calorie restriction, or inflammation, so it’s not entirely surprising that we see them after vaccination too.
Realizing the gaping scientific hole when it comes to our knowledge of vaccines and reproductive health, NIH has recently announced new funding mechanisms and research initiatives so that researchers can better understand the relationship (if one exists) between vaccination, reproductive health, and fertility. We’ll continue updating posts as these new data come out.
Is the COVID-19 vaccine safe if you're currently pregnant?
These recommendations are backed by epidemiological data from the CDC. Through its v-safe and VAERS programs, the CDC is closely monitoring post-vaccine side effects and outcomes in people who choose to participate. They published their findings on over 35,691 pregnant people in the New England Journal of Medicine (one of the most respected scientific journals out there!):
- While rumors sprung up about a connection between miscarriages and COVID-19 vaccination in the UK (a claim that has since been debunked), researchers found no differences in pregnancy outcomes like miscarriages between pregnant people who did and did not get the COVID-19 vaccine — as well as no differences in the rate of pregnancy complications (like gestational diabetes or hypertension) or neonatal factors (like preterm birth or abnormalities).
- They also found that the side effect profile of vaccines didn’t meaningfully differ based on whether someone was pregnant at the time of vaccination — while pregnant people were more likely to report injection-site pain, they were less likely to report things like headache, chills, and fever.
This is in contrast to what's been observed when comparing pregnant people with and without COVID-19:
- Two studies (one from England and one that evaluated people from 18 different countries) observed that pregnant people who are infected with COVID-19 are more likely to experience negative maternal and neonatal outcomes and increased risk of death for both the birthing person and fetus.
- A UC San Francisco study that followed over 200,000 live births found that people who got COVID-19 at any time during their pregnancy had a 60% higher risk of very preterm birth (before 32 weeks).
- An analysis of over 480,000 births found that having COVID-19 during delivery was associated with a higher risk of a whole bunch of negative outcomes including preterm labor and delivery, death, ICU admission, and sepsis, among others.
- A meta-analysis of existing studies found that COVID-19 infection during pregnancy is associated with preeclampsia, preterm birth, and stillbirth. There’s also evidence suggesting that these outcomes are seen more frequently in people who had severe versus mild COVID-19.
- And, like we mentioned earlier, pregnant people are also 5x more likely to have severe symptoms if they contract COVID-19 relative to non-pregnant people.
So, while COVID-19 vaccines seem to have no effect on pregnancy outcomes (further confirmed by this meta-analysis), COVID-19 infection likely does have negative effects.
Mounting evidence also suggests that the earlier on in a pregnancy someone gets vaccinated, the more likely they are to pass antibodies on to their newborns.
- In a study of 27 people who got the vaccine during their third trimester, researchers found that newborns of people who got vaccinated earlier were more likely to have COVID-19 antibodies, as compared to newborns of people who got vaccinated close to the time of delivery.
- A larger study of 85 pregnant people who got vaccinated also found that those who got vaccinated during the second trimester were more likely to pass on antibodies to their newborns as compared to people who got vaccinated in the third trimester.
- A recent meta-analysis including all published studies to date confirm these findings: that the earlier someone got the vaccine during pregnancy, the more likely their newborn was to have COVID-19 antibodies.
Even before we had this large-scale data from the CDC on pregnancy and COVID-19 vaccines, there were many reasons to believe that the vaccine would be safe for all, regardless of whether or not someone is pregnant (and regardless of any circulating myths):
- Numerous vaccines have been given to pregnant and breastfeeding/chestfeeding people for decades, without any negative effect on fertility-related outcomes.
- Based on the completed clinical trial phases thus far, there aren’t any signals to suggest that the effect of the vaccine would be different for people who are pregnant.
- We now have data from a meta-analysis to confirm what we’ve seen regarding safety in the clinical trial phases: that side effects of the vaccine are the same in people who are versus aren’t pregnant.
- Likewise, based on completed trial phases looking at the effects of the vaccine in cells and in lab animals, there aren't any signals to suggest the vaccine would have any effect on fetal or infant development. (Specifically, there were no detected abnormalities in offspring of lab rats given the COVID-19 vaccine during pregnancy.)
Why are there so many questions about the COVID-19 vaccine and safety for pregnant people?
While clinical trials for the COVID-19 vaccine including pregnant people are currently being run by vaccine manufacturers and by the National Institutes of Health, this wasn't the case at first: People were not allowed to participate if they were pregnant or breastfeeding/chestfeeding at enrollment.
Excluding pregnant people from clinical trials is a standard practice researchers use to avoid unanticipated harmful effects on a developing fetus. This can make things very difficult because there is often very little data on whether medications and vaccines are safe for pregnant people — but it doesn't mean that a vaccine or medication is automatically dangerous for pregnant people. (For more on the ethics of including pregnant people in trials, we’d recommend ACOG’s committee opinion on the topic.)
Is the COVID-19 vaccine safe if you're currently breastfeeding/chestfeeding?
Breastfeeding/chestfeeding people were excluded from the vaccine trials that we currently have data on, meaning we haven’t yet seen firsthand how the vaccine affects breastfeeding/chestfeeding people and their babies. But we have reason to believe that the vaccine is safe for these groups because there isn’t a scientifically plausible mechanism by which the vaccine could cause harm. In fact, getting the vaccine while breastfeeding/chestfeeding could potentially protect babies from getting COVID-19.
According to a December 2020 statement from the Academy of Breastfeeding Medicine (ABM), it is likely that the antibodies created in response to the COVID-19 vaccine would transfer into breast/chest milk, providing the baby with these antibodies and strengthening their ability to counter COVID-19 if they were exposed. Some initial studies based on small samples do indeed find COVID-19 antibodies in breast/chest milk of people who previously had the virus, and others have now found COVID-19 antibodies in breast/chest milk of people who got vaccinated. We’re still waiting on data on how those antibodies may (or may not) protect and affect breastfeeding/chestfeeding babies.
More generally, of all commonly administered vaccines, there are only two that the CDC recommends holding off on while breastfeeding/chestfeeding — the smallpox and yellow fever vaccines, both of which contain a weakened version of the actual virus (unlike the mRNA COVID-19 vaccines, which don’t contain any trace of live virus).
Bottom line: Should you get the COVID-19 vaccine?
All the available data suggests that the COVID-19 vaccines that are FDA-approved or authorized for emergency use are very safe and effective for the vast majority of people. Though not enough time has elapsed since the beginning of clinical trials, and pregnant and breastfeeding/chestfeeding people were initially excluded from those trials, the data that’s been published so far shows no adverse effects on fertility and fetal/infant development.
Based on these published findings and data from earlier trial phases, other vaccines, and our knowledge of how mRNA and adenovirus vaccines work, multiple influential health organizations agree that COVID-19 vaccines likely will have no negative effects on reproductive health and related outcomes, and therefore have suggested that people who are pregnant, breastfeeding/chestfeeding, or trying to conceive get the vaccine.
It's important for those who choose not to get vaccinated at this time to embrace other safety measures, like mask wearing, social distancing, hand washing, and avoiding large gatherings. For all of us, it's crucial to check in with ourselves physically and mentally as we continue to deal with the realities of a global pandemic.
This article was medically reviewed by Dr. Jane van Dis, MD, FACOG and Dr. Edu Hariton, MD, MBA. Dr. van Dis is a practicing OB-GYN, volunteer clinical faculty at USC Keck School of Medicine where she serves on the Gender Equity in Medicine and Science Committee, CEO of Equity Quotient, co-founder of OB Best Practice, and co-founder of TIME'S UP Healthcare. Dr. Hariton is an OB-GYN and reproductive endocrinology and infertility fellow at the University of California in San Francisco.