This story first appeared at ProPublica. ProPublica is a Pulitzer Prize-winning investigative newsroom. Sign up for The Big Story newsletter to receive stories like this one in your inbox.

Even before the COVID-19 vaccine was authorized, there was a plan to discredit it.

Leaders in the anti-vaccination movement attended an online conference in October 2020 — two months before the first shot was administered — where one speaker presented on “The 5 Reasons You Might Want to Avoid a COVID-19 Vaccine” and another referred to the “untested, unproven, very toxic vaccines.”

But that was only the beginning. Misinformation seeped into every corner of social media, onto Facebook feeds and into Instagram images, pregnancy apps and Twitter posts. Pregnant people emerged as a target. A disinformation campaign preyed on their vulnerability, exploiting a deep psychological need to protect their unborn children at a moment when so much of the country was already gripped by fear.

“It’s just so powerful,” said Imran Ahmed, the founder and chief executive officer of the U.S. nonprofit Center for Countering Digital Hate, which tracks online disinformation.

A majority of the disinformation came from a group of highly organized, economically motivated actors, many of them selling supplements, books or even miracle cures, he said. They told people the vaccine may harm their unborn child or deprive them of the opportunity to become parents. Some even infiltrated online pregnancy groups and asked seemingly harmless questions, such as whether people had heard the vaccine could potentially lead to infertility.

The Center for Countering Digital Hate found that nearly 70% of anti-vaccination content could be traced to 12 people, whom they dubbed The Disinformation Dozen. They reached millions of people and tested their messaging online, Ahmed said, to see what was most effective — what was most frequently shared or liked — in real time.

“The unregulated and unmoderated effects of social media where people are allowed to spread disinformation at scale without consequences meant that this took hold very fast,” Ahmed said. “That’s had a huge effect on women deciding not to take the vaccine.”

Some people, such as Robert F. Kennedy Jr., seized on the initial dearth of research into vaccines in pregnant people. “With no data showing COVID vaccines are safe for pregnant women, and despite reports of miscarriages among women who have received the experimental Pfizer and Moderna vaccines, Fauci and other health officials advise pregnant women to get the vaccine,” Kennedy posted in February 2021 on Facebook. Kennedy did not respond to requests for comment.

Disinformation flourished, in part, because pregnant people were not included in the vaccine’s initial clinical trials. Excluding pregnant people also omitted them from the data on the vaccine’s safety, which created a vacuum where disinformation spread. Unsure about how getting the shots might affect their pregnancy — and without clear guidance at the time from the Centers for Disease Control and Prevention — pregnant people last year had some of the lowest vaccination rates among adults.

The decision to delay or avoid vaccination, often made out of an abundance of caution and love for the baby growing inside of them, had dire consequences: Unvaccinated women who contracted COVID-19 while pregnant were at a higher risk of stillbirths — the death of a fetus at 20 weeks or more of pregnancy — and several other complications, including maternal death.

Although initial clinical trials did not include pregnant people, the Food and Drug Administration ensured that vaccines met a host of regulatory safety standards before authorizing them. Citing numerous studies that have since come out showing the vaccine is safe, the CDC now strongly recommends that people who are pregnant, breastfeeding or planning to become pregnant get vaccinated. The major obstetric organizations, including The American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine, also urge pregnant people to get vaccinated.

But two and a half years into the pandemic, misinformation is proving resilient.

A May 2022 Kaiser Family Foundation poll found more than 70% of pregnant people or those planning to become pregnant believed or were unsure whether to believe at least one of the following popular examples of misinformation about the COVID-19 vaccine: that pregnant people should not get vaccinated; that it’s unsafe to get vaccinated while breastfeeding; or that the vaccine has been shown to cause infertility. None of which are true.

Dr. Laura Morris, a University of Missouri, Columbia family physician who delivers babies, has heard all those falsehoods and more from her patients. She has long relied on science to help encourage them to make well-informed decisions.

But when officials rolled out the vaccine, she found herself without her most powerful tool, data. The disinformation didn’t have to completely convince people that the vaccine was dangerous; creating doubt often was sufficient.

“That level of uncertainty is enough to knock them off the path to accepting vaccination,” Morris said. “Instead of seeing vaccines as something that will make them healthier and improve their pregnancy outcomes, they haven’t received the right information to make them feel confident that this is actually healthy.”

Before COVID-19, Morris typically saw one stillbirth every couple of years. Since the pandemic started, she said she has been seeing them more often. All followed a COVID-19 diagnosis in an unvaccinated patient just weeks before they were due. Not only did Morris have to deliver the painful news that their baby had died, she also told them that the outcome might have been different had they been vaccinated. Some, she said, felt betrayed at having believed the lies surrounding the vaccine.

“You have to have that conversation very carefully,” Morris said, “because this is a time where the people are feeling awful and grieving and there’s a lot of guilt associated with these situations that’s not deserved.”

In December 2021, the Federation of State Medical Boards found a proliferation of misinformation about COVID-19 among health care workers. Two-thirds of state medical boards reported an increase in complaints about misinformation, but fewer than 1 in 4 of them reported disciplining the doctors or other health care workers.

Dr. Sherri Tenpenny, an osteopath, was the speaker at the October 2020 conference who called the COVID-19 vaccine “toxic.” She later testified at an Ohio state House Health Committee hearing on the Enact Vaccine Choice and Anti-Discrimination Act. She falsely claimed that the vaccine could magnetize people. “They can put a key on their forehead, it sticks,” she said. “They can put spoons and forks all over them, and they could stick.” She also questioned the connection between the vaccine and 5G towers.

Despite her statements, the State Medical Board of Ohio has not taken any disciplinary action against her. Her medical license remains active. Tenpenny did not respond to requests for comment.

It’s difficult to know exactly how many doctors were disciplined, a term that can mean anything from sending them letters of guidance to revoking their license. State medical boards in some cases refused to disclose even the number of complaints received.

Some records were made public if formal disciplinary action was taken, as in the case of Dr. Mark Brody. The Rhode Island physician sent a letter to his patients that the state medical board determined contained several falsehoods, including claims that “there exists the possibility of sterilizing all females in the population who receive the vaccination.” The Rhode Island Board of Medical Licensure and Discipline reprimanded him for the letter, then suspended his medical license after other professional conduct issues were uncovered. He surrendered his license in December.

Brody said in an interview that he stands by the letter. He said the word “misinformation” has been politicized and used to discredit statements with which people disagree.

“This term doesn’t really apply to science,” he said, “because science is an ever-evolving field where today’s misinformation is tomorrow’s information.”

The Washington Medical Commission has received more than 50 complaints about COVID-19 misinformation since the start of the pandemic, a spokesperson there said. California does not track misinformation complaints specifically, but a Medical Board of California spokesperson said that, in that same time period, the group received more than 1,300 COVID-19-related complaints. They included everything from fraudulent promotion of unproven medications to the spreading of misinformation.

“We were certainly surprised that more than half of boards said they had seen an increase in complaints about false or misleading information,” said Joe Knickrehm, vice president of communications for the Federation of State Medical Boards, which in April adopted a policy stating that “false information is harmful and dangerous to patients, and to the public trust in the medical profession.”

Other groups, including The American College of Obstetricians and Gynecologists, warned doctors about spreading misinformation. In October, the organization asked its members to sign a letter endorsing the COVID-19 vaccine, writing that “the spread of misinformation and mistrust in doctors and science is contributing to staggeringly low vaccination rates among pregnant people.” But the letter was never published. “We didn’t achieve the numbers we had hoped,” a spokesperson for the organization said, “and did not want to release it if it was not going to be compelling to patients.”

The fact that some medical professionals have been spreading disinformation or failing to engage with their patients about the vaccine is profoundly disappointing, said Dr. Rachel Villanueva, a clinical assistant professor of obstetrics and gynecology at New York University’s Grossman School of Medicine and president of the National Medical Association, which represents Black doctors.

Research has shown that hearing directly from a health care provider can increase the likelihood that patients get vaccinated. And doctors, Villanueva said, have a responsibility to tell their patients the benefits of getting vaccinated and the risks of choosing not to. She has explained to her patients that although the vaccine development program was named Operation Warp Speed, for example, manufacturers followed proper safety protocols.

“Before COVID, there already existed a baseline distrust of the health care system, especially for women of color, feeling marginalized and feeling dismissed in the health care system,” she said. “I think that just compounded the already lack of confidence that existed in the system.”