If there’s one thing you can always count on, it’s gravity, taxes, and anti-vaccine activists warning that vaccines will “destroy fertility.” Long before COVID-19 showed up, similar scare stories surrounded HPV, polio, and even tetanus shots. So when mRNA vaccines arrived, it was almost guaranteed that someone would eventually shout, “They’ll make women infertile!”
Science-Based Medicine has been pointing out this exact pattern for years: new vaccine arrives, conspiracy machine cranks up, and suddenly social media is full of dramatic claims about miscarriages, infertility, and “attacks on womanhood.” The infertility rumor around COVID-19 vaccines is just the latest sequel in a very old franchise.
In this article, we’ll unpack where the COVID-19 infertility myth came from, why the proposed biological mechanism doesn’t hold up, and what the best available data actually shows about fertility, periods, pregnancy, and the vaccines. We’ll also look at why these myths spread so easilyand how to respond when a friend says, “I’m scared the shot will make it harder to have kids.”
Why fertility scare stories always follow vaccines
A very old playbook
Anti-vaccine campaigns have a long history of aiming directly at reproductive fears. If you can convince people that a vaccine threatens their ability to have children, you don’t just raise doubtyou hit a primal fear and a powerful cultural value at the same time.
We’ve seen versions of this with:
- Rumors that HPV vaccines cause premature ovarian failure.
- Claims that tetanus vaccines were secretly laced with agents to cause miscarriages in low-income countries.
- Stories that routine childhood vaccines “sterilize” young girls.
Every time, careful investigation showed no evidence of a real fertility problem. But the pattern stuck: if you’re trying to frighten the public, “they’re coming for your children” and “they’re taking away your ability to have children” are emotionally supercharged talking points.
COVID-19 vaccines were an obvious new target
When COVID-19 vaccines rolled out at unprecedented speed, people had reasonable questions. mRNA sounded high-tech and unfamiliar. Social media, meanwhile, rewarded hot takes, not nuance. Into that environment walked a rumor: that the spike protein in COVID-19 vaccines could somehow train the immune system to attack a protein needed for placenta formation, allegedly causing miscarriages and infertility.
That storyline checked all the boxes for viral misinformation: it sounded “scientific,” it mentioned proteins and the immune system, and it played directly on fears about pregnancy and future fertility. It was almost tailor-made for antivaxxers who had been using fertility myths for decades.
The syncytin-1 myth: How the infertility rumor was born
The petition that launched a thousand Facebook posts
The COVID infertility myth really took off after a petition to the European Medicines Agency raised a hypothetical concern: what if antibodies created by the vaccines against the SARS-CoV-2 spike protein also attacked a human protein called syncytin-1? Syncytin-1 is important in forming the placenta, so the claim was that the immune response could somehow interfere with pregnancy.
Key detail: the petition did not provide evidence that this actually happens. It proposed a speculative “what if” scenario. But by the time the idea had traveled through Facebook, Instagram, and YouTube, the careful “what if” had turned into “the vaccine will make women infertile.” That’s not how evidence-based medicine worksbut it is exactly how misinformation works.
Why the biology doesn’t add up
The scientific problem with this theory is straightforward: the spike protein and syncytin-1 are not meaningfully similar. Their amino acid sequences are different enough that antibodies against the spike protein have no reason to latch onto syncytin-1 or attack the placenta.
If the immune system really were confused in this way, we’d expect to see:
- A dramatic spike in infertility after infection with COVID-19 itself (which exposes people to much more spike protein than the vaccine).
- Higher rates of miscarriage or problems with placental development in vaccinated people compared with unvaccinated people.
That’s not what the data show. Instead, large studies and real-world pregnancy outcomes have repeatedly found no signal that COVID-19 vaccines cause infertility or miscarriages, while COVID-19 infection can increase risks during pregnancy. In other words, the biological theory was weak from the startand the real-world evidence has only made it weaker.
What the evidence actually says about COVID-19 vaccines and fertility
People trying to conceive naturally
Surveys and cohort studies following people who were trying to conceiveeither with or without fertility tracking appshave looked at how long it took them to get pregnant and whether vaccination made any difference. The result: no meaningful difference in fertility between vaccinated and unvaccinated people when you account for age and other factors.
A systematic review and meta-analysis that pulled together data from multiple studies found no negative effect of vaccination on conception rates or pregnancy outcomes for individuals trying to conceive naturally. The timing of the shot, the type of vaccine (including mRNA), and the number of doses didn’t translate into reduced chances of becoming pregnant.
IVF and fertility clinic data
Fertility clinics provide particularly useful data because they track things very closely: egg counts, embryo quality, implantation rates, biochemical pregnancy rates, and live birth rates. Studies comparing treatment cycles in vaccinated versus unvaccinated patients have consistently found:
- No reduction in the number of eggs retrieved.
- No difference in fertilization rates.
- Similar embryo quality and implantation rates between groups.
- No increased risk of miscarriage among vaccinated patients.
In other words, if vaccines were secretly sabotaging fertility, IVF clinics would be the first to spot itand they’re just not seeing that pattern.
Male fertility and sperm
The infertility myth is often framed as a “female” problem, but anti-vaccine rumors haven’t spared men either. Some social media posts warned that vaccines would wreck sperm counts, lower testosterone, or otherwise compromise male fertility.
However, studies that measured sperm counts, motility, and other parameters before and after vaccination found no clinically significant changes. In some small studies, average values even ticked upward slightly after vaccination, but that’s more likely random fluctuation than a magic fertility booster.
Professional organizations and public health agencies have concluded that there is no evidence COVID-19 vaccines harm male fertility. That matches what large populations are showing in real life: vaccinated men are still becoming fathers with no obvious problems.
Pregnancy, miscarriage, and menstrual changes
Pregnancy and miscarriage rates after vaccination
Another flavor of the infertility myth focuses on miscarriageclaims that vaccines cause early pregnancy loss or stillbirth. This understandably terrifies people who are pregnant or trying to become pregnant.
But surveillance systems and large registry studies tracking tens of thousands of pregnancies have found that:
- Miscarriage rates among vaccinated pregnant people are within the expected range seen before the pandemic.
- No higher rate of stillbirths has been linked to vaccination.
- Outcomes such as preterm birth, low birth weight, and congenital anomalies do not appear increased by vaccination.
By contrast, COVID-19 infection itself has been associated with higher risks of severe illness, ICU admission, preterm birth, and other complications in pregnant people. So if you’re playing the odds, avoiding vaccination leaves you exposed to the riskier option.
Menstrual changes don’t equal infertility
Many people have reported changes in their periods after vaccination: heavier or lighter bleeding, cycles a bit earlier or later, or spotting when they didn’t expect it. Research suggests that COVID vaccination can be associated with short-term menstrual changes in some people, likely due to temporary immune and hormonal crosstalk.
Importantly:
- These changes tend to be small and self-limited, usually resolving within a cycle or two.
- There is no evidence that these temporary changes translate into long-term fertility problems.
- Menstrual cycles can be influenced by many thingsstress, illness, weight changes, sleep patternsso it’s not surprising to see some shifts during a pandemic.
Talking honestly about menstrual changes is important; ignoring them only feeds mistrust. But acknowledging that something happens is not the same as saying “this causes infertility.” That leap is exactly where misinformation jumps the tracks.
COVID-19 infection is the real threat to fertility and pregnancy
How severe COVID-19 affects pregnant people
While vaccines keep getting blamed for hypothetical harms, the virus itself has caused very real ones. COVID-19 infection during pregnancy has been linked with:
- Higher risk of hospitalization and ICU admission.
- Greater need for mechanical ventilation in severe cases.
- Increased risk of preterm birth and certain pregnancy complications.
Getting vaccinated dramatically lowers the risk of severe COVID-19. For pregnant people, that risk reduction matters not only for their own health, but also for the baby’s well-being, since maternal illness and inflammation can affect the pregnancy.
Protecting both parent and baby
One of the underappreciated benefits of vaccination during pregnancy is that it can provide antibodies to the baby through the placenta and later through breast milk. That means newborns get some temporary protection during a period when they’re too young to be vaccinated directly.
Medical and public health organizations around the world have repeatedly emphasized that, based on the best available evidence, COVID-19 vaccines are safe and effective for people who are pregnant, breastfeeding, or planning pregnancy. That doesn’t mean zero risknothing in medicine is truly zero-riskbut it does mean the benefits far outweigh the known risks, especially when compared with getting COVID-19 while pregnant.
Why infertility myths stickand how to respond
Why these stories feel so convincing
Even when the data are clear, infertility myths can still feel emotionally powerful. A few reasons:
- They’re anchored in fear, not facts. Wanting children (or wanting the option) is deeply personal. Threaten that, and logic often takes a back seat.
- They use scientific-sounding language. Throw in words like “protein,” “placenta,” or “antibodies,” and a claim can sound legitimate even if the underlying science is shaky.
- They spread through trusted networks. People often hear these rumors from friends, family, or influencers they already trust, not from obvious trolls.
- Algorithms love drama. Content that frightens or angers people tends to get more engagement, which means more visibilityeven if it’s wrong.
Once a myth lodges in people’s minds, it’s not enough to simply say, “That’s false.” You have to acknowledge the underlying worry, provide clear explanations, and give people something more reassuring to hold on to.
How to talk with someone who’s worried about fertility and vaccines
If a friend or family member says, “I’m scared the vaccine will make it harder to get pregnant,” here are some practical, science-aligned ways to respond:
- Start with empathy. “I get why that would scare you. Fertility is a huge deal.”
- Share what experts actually see. Explain that fertility clinics, obstetricians, and researchers analyzing thousands of cycles and pregnancies are not seeing lower fertility or more miscarriages in vaccinated people.
- Clarify the origin of the myth. Talk about the speculative syncytin-1 idea and how it didn’t hold up under scrutiny.
- Contrast hypothetical risks with real ones. Point out that COVID-19 infection, especially in pregnancy, is a known, measurable risk, while the infertility fear remains unsupported.
- Encourage talking to a trusted clinician. Suggest they discuss their specific situation with an OB-GYN, midwife, or fertility specialist who keeps up with the latest data.
The goal isn’t to “win an argument,” but to give people enough accurate information and emotional space to make decisions they can feel comfortable with later.
Real-world experiences: how the infertility myth shows up in everyday life
To understand the impact of the infertility myth, you don’t need to look any further than a busy OB-GYN clinic or fertility practice. The rumors that started with a speculative petition have turned into real-world anxiety that clinicians now manage on top of everything else.
Picture a typical day in a large urban OB-GYN office. The waiting room is full: a couple there for their first prenatal visit, a woman getting her annual exam, someone else following up after a miscarriage. Somewhere in that mix is usually a patient who leans in and asks quietly, “Be honestcould the COVID shot make it harder for me to get pregnant?”
Many clinicians describe having that conversation over and over again. They pull up charts, explain how the vaccines work, talk about how the immune system sees the spike protein, and walk through the big studies that show no effect on fertility. Some will point out that their own staff were vaccinated and have gone on to have healthy pregnancies and babies. That kind of personal, concrete reassurance often lands better than raw data alone.
Fertility specialists tell similar stories. In IVF clinics, patients sometimes worry that getting vaccinated will “ruin” a carefully timed cycle. Providers explain that vaccination doesn’t appear to alter egg quality, hormone levels, or implantation rates, and that they’re watching their own clinic outcomes closely. Many clinics have now seen hundreds or thousands of vaccinated patients go through retrievals, transfers, and pregnancies with no sign of decreased success rates. That real-world track record is powerfulespecially when it comes from the very people whose job is to help patients have children.
There are also stories from patients who delayed vaccination because of infertility fears and then later wished they had made a different choice. Some got COVID-19 while pregnant and ended up in the hospital, frightened for themselves and their babies. Others watched friends or family members go through severe COVID-19 while they themselves stayed unvaccinated out of worry about fertility. For a few, the turning point was seeing fellow patients in the maternity ward who had been vaccinated, delivered healthy babies, and recovered faster from mild infections.
On the flip side, there are countless quiet, everyday examples of people who got vaccinated, went on with their lives, and had the children they’d hoped for. They don’t make headlines, but they matter. A woman who received her first dose while trying to conceive and found out she was pregnant the next month. A nurse who got boosted during her fertility treatments and later sent a photo of her newborn to the clinic staff. A couple who postponed their second dose until after embryo transfer, then later read the data and realized they hadn’t needed to wait.
These lived experiences don’t replace rigorous studies, but they line up with them. When you combine personal stories from clinics and communities with the large body of evidence from epidemiology, registries, and randomized trials, the picture is consistent: COVID-19 vaccines are not causing infertility in women or men. What they are doingimperfectly, but meaningfullyis reducing severe disease, hospitalizations, and pregnancy complications linked to COVID-19 itself.
The infertility myth will probably linger online for a long time; once a rumor escapes into the wild, it’s hard to delete it from the internet’s memory. But clinicians, scientists, and patients now have something they didn’t have back in 2020: years of real-world data, millions of pregnancies, and countless examples of vaccinated people starting or growing their families. That lived reality is one of the strongest counters to a fear-based narrative.
The bottom line
From a Science-Based Medicine perspective, the infertility claims about COVID-19 vaccines look like what they’ve always been: a recycled myth dressed up in new vocabulary. The proposed mechanism doesn’t hold up biologically, and the actual datafrom fertility clinics, pregnancy registries, and large population studiessimply don’t show that vaccinated people are becoming infertile.
That doesn’t mean people’s fears are silly or irrelevant. Fertility and pregnancy are among the most sensitive topics in medicine, and it’s understandable to be cautious. But caution should be based on evidence, not on speculative petitions and viral memes.
The weight of the science so far is clear: COVID-19 vaccines do not make females infertile. They do, however, lower the risk of severe COVID-19, especially during pregnancy, and help protect both parents and babies. Antivaxxers were always going to claim otherwisebut you don’t have to believe them.
