A doctor gives a vaccination to a pregnant person holding their stomach

There’s no evidence COVID-19 vaccines hurt fertility. Here’s what’s fueling the myth

COVID-19 vaccines are both safe and effective for pregnant people and those who plan to become pregnant, according to all of the data gathered by researchers so far. But the baseless concern or belief that they could hurt a person’s ability to conceive and deliver a healthy child has influenced many in choosing not to get a shot.

In August, the Centers for Disease Control and Prevention officially recommended that pregnant people get vaccinated against COVID-19, in part because they are at a higher risk of becoming severely ill from the disease compared to non-pregnant people. Those who are attempting to conceive or are breastfeeding should also get their shots, the CDC has said. In addition, there is some evidence that the virus — not the vaccine — could potentially negatively impact sperm production and testicular function.

But these facts haven’t been enough to convince everyone. Some holdouts might say they’re waiting for more information on the potential long-term side effects of these shots — so far, researchers haven’t found any — or for official approval by the Food and Drug Administration, like Pfizer’s was given last month.

Others seem opposed to vaccination, period. Whether peddled by anti-vaccination groups online or spread by word-of-mouth, experts say misinformed skepticism around fertility is nothing new.

“It’s important to remember that lies about vaccines and fertility are a standard anti-vaccine talking point,” said Dr. Jen Gunter, an OB/GYN and medical writer.

Misinformation and disinformation around COVID-19 vaccines have also drawn attention to legitimate problems, like the way pregnant people — and, sometimes, women in general— have been excluded from some drug research and clinical trials, ostensibly in the name of safety. Those decisions can lead to knowledge gaps, which bad actors can weaponize to further their agendas.

Here’s a look at the tangled history of fertility fears and vaccine skepticism, and how this moment could be an opportunity to address the consequences of leaving pregnant people, women and their unique health concerns out of medical trials and conversations.

How scare tactics exploit our fertility anxieties

Preying on concerns around reproductive health has long been an effective way to turn people against vaccination, experts say. Fertility is a personal, often emotional topic, and having kids is integral to many people’s visions of their own futures. False anti-vaccination talking points often take advantage of that emotion, as well as the desire to ensure you’re not doing anything that could jeopardize chances of having a family.

“So if you’re trying to scare people, it’s a really good one to leverage,” said Devon Greyson, an assistant professor at the University of British Columbia School of Population and Public Health. “But also, if you’re just [a worried person,] it’s something you might worry about.”

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Reproductive endocrinologist Dr. Albert Hsu works with patients who have faced and are seeking to overcome barriers to conception. Around 10 to 15 percent of the global population, he said, grapples with infertility. Hsu, who is based at the University of Missouri, estimates that between 50 to 60 percent of the patients at his clinic have not yet gotten vaccinated.

Among the false claims about COVID-19 vaccines circulating online, many specifically seek to undermine trust in Pfizer and Moderna’s mRNA-based shots, despite the decades of research backing them up. Though the claims may be specific to these vaccines, they’re part of a much larger, persistent infrastructure of false information.

“If you look more broadly at vaccine hesitancy and resistance over time, we really see fertility fears recycled from vaccine to vaccine, even among vaccines that use completely different underlying science,” Greyson said.

In the first decade after they were rolled out in North America in the mid-2000s, HPV vaccines were subject to fertility-based fear mongering with no scientific credibility, Greyson said. Research has never found a link between these shots and negative impacts on reproductive health — in fact, they protect recipients against certain cancers that can cause fertility issues. This was another phenomenon largely due to the fact the shots were initially marketed specifically to teenage girls, they added, and that HPV itself is generally associated with reproductive organs.

On a global scale, particularly in formerly colonized nations, vaccines may be associated with fertility concerns due in part to the historical reality that those in power would forcibly sterilize people “without consent, often under the auspices of medical care,” Greyson said. The lingering distrust within communities can exacerbate vaccine hesitancy when reignited by misleading information spread online or by word-of-mouth.

In the United States, hesitancy may be informed by a comparable history of medical abuse — which also included forced sterilization — in some communities of color, said Alexandra Minna Stern, the Carroll Smith-Rosenberg Collegiate Professor of History, American Culture and Women’s and Gender Studies at the University of Michigan.

Fertility and reproduction is “symbolically and physically connected to the future — the future of certain communities and whether or not they’re being supported and can thrive, or whether or not they’re being curtailed and controlled,” Stern said.

When Hsu asks his vaccine-hesitant patients more about their concerns, many tell him that they want to “wait for more data,” he said. Rather than try to change their minds, he often encourages patients who don’t want to get the vaccine before or during pregnancy to at least consider getting it once they’ve given birth.

“It’s one of those things that takes time. It’s one of those things where telling people doesn’t work,” he said. “It really requires asking them, getting their opinions and trying to figure out where you can go together.”

What vaccine studies do measure — and what they don’t

Back in January, the CDC’s guidance for pregnant people asserted that mRNA vaccines were “unlikely” to pose a specific risk for that population while acknowledging that “actual risks to pregnant individuals and their fetuses” were unknown because the vaccines had not been studied in that population, according to an analysis in JAMA. At that time, the agency said that pregnant people should discuss it with their doctors.

Pregnant people are generally excluded from vaccine trials, including the ones for COVID-19 shots (although some participants did get pregnant after receiving their doses). Greyson said that some drugs on the market for decades were never even tested in women prior to their approval, which in some cases can have implications for their performance.

But we do have growing evidence to back up these vaccines. A recent, not-yet-peer-reviewed analysis of data from the Centers for Disease Control and Prevention’s v-safe COVID-19 Vaccine Pregnancy Registry, a voluntary survey that tracks outcomes in pregnant people who get vaccinated against the disease, found a comparable miscarriage rate between people who received the either Pfizer or Moderna mRNA COVID-19 vaccine before 20 weeks of pregnancy and the general population. That means that no association between vaccination and pregnancy loss was observed.

Research efforts that evaluate vaccines after they’ve made it to market also track incidences of expected side effects, as well as any potential adverse reactions to vaccination. For instance, the CDC has said that all women under 50 years of age, regardless of pregnancy status, “should be aware of the rare but increased risk for thrombocytopenia syndrome (TTS)” associated with Johnson & Johnson’s shot. The condition — which is unrelated to fertility — is when someone has both blood clots and low platelet counts, and the chances of that happening to a vaccine recipient are extremely slim. As of April 2021, there were just seven cases reported per million doses administered among adult women under 50.

But there is a question that hasn’t been addressed by those efforts: Do the vaccines affect menstruation?

Vaccine studies aren’t designed to track menstrual irregularity, which would require a few months of data before the trial itself in order to establish a baseline. That doesn’t mean they “couldn’t or shouldn’t be in the future,” Gunter said.

In the case of COVID-19 vaccines, more data is on the way. The National Institutes of Health announced in August that it would distribute over $1 million across several institutions to support research into any possible links between those vaccines and menstrual changes.

Should vaccine researchers track menstruation?

In the spring, multiple reports surfaced — particularly on social media — from people who said that their period had changed in some way, like arriving later or with a heavier flow than usual, after receiving a COVID-19 shot.

We can’t really draw any conclusions from that “biased sample,” Gunter said, because those reports themselves are anecdotal. Only a formal research effort can confirm or deny the connection between vaccination and menstrual changes — it’s impossible without one to know how many people experienced irregularity compared to those who didn’t.

But there is a biological explanation as to how irregular periods could occur post-vaccination. The endometrium, or the uterine lining that sheds during menstruation, is part of the broader network for the body’s immune system, explained Gunter, who broke down this connection in a Substack piece in April.

“Just like you might get a lymph node swelling after a vaccine, you could potentially get changes in the lining of the uterus,” she added. “And just like your lymph node is not going to be permanently swollen — or you’re not going to permanently have a fever from getting your vaccine, also an immune side effect — you’re not going to have permanent changes” to your period.

People generally don’t panic when they develop a fever after getting a vaccine because they’ve been warned about that side effect ahead of time. (A small increased risk in pregnancy loss and birth defects has been linked to high fevers in early pregnancy in animal studies, according to the University of Chicago. Experts recommend taking Tylenol or another safe fever reducer recommended by your physician if necessary post-vaccination.)

Not having similar information on menstruation — if there is a connection — denies vaccine recipients a similar peace of mind. And when these reasonable talking points are co-opted by anti-vaccination groups or misunderstood by individuals, they can become a breeding ground for misinformed fertility fears.

That’s “a tricky rumor to debunk,” Greyson said, “because it intertwines legitimate concerns about women’s health and fertility research with unsupported theories and false claims of causality.”

Fertility myths offer false certainty

Dr. Seema Yasmin, director of the Stanford Health Communication Initiative, believes the “blanket exclusion” of pregnant people from clinical trials for COVID-19 vaccines wasn’t a “smart move,” and that more could have been done to safely them.

The false information that can take hold with the help of those kinds of research gaps points directly to the “much deeper issue” of a lack of emphasis on reproductive health, rooted in sexism, she added.

“We have deprioritized women’s health. We have not put sufficient resources, including money, time and all of those investments into understanding reproductive health,” Yasmin said. “And then we pay the price for it in these particular ways.”

Misinformation and disinformation have a big advantage: They offer a false sense of certainty, making them hard to combat. Real science, on the other hand, shies away from absolutes and focuses instead on what’s known to be true based on evidence.

It would be ideal, Hsu said, if researchers could make the “declarative statement” that COVID-19 vaccines are “100 percent safe in all populations forever and ever.” But that’s not how science works — there’s just no way to prove or disprove that assertion.

“So-called ‘alternative medicine’ has confidence, they speak in absolutes,” Dr. Jen Gunter said. “But when you have no studies and you’re making stuff up, of course you can [do that].”

Rebecca Newman contributed reporting to this story.