THE FACTS: A false conspiracy theory circulated on social media suggesting that people who haven’t been vaccinated against COVID-19 can experience changes in their cycle or miscarriages, solely by being physically close to a person who received the vaccine.

On Tuesday, The Associated Press reported on a private school in Miami that warned teachers and staff against taking the COVID-19 vaccine, citing the baseless theory.

One false Instagram post accused vaccinated people of “negatively impacting women’s menstrual cycles” and falsely claimed that miscarriages were “up 400%.”

Multiple social media posts referred to the baseless theory as a form of “shedding,” including an Instagram post that inaccurately blamed “extended or extremely heavy cycles” on “being around people who are recently vaccinated and shedding.”

Dr. Jen Gunter, an obstetrician-gynecologist and author, told the AP in a call that the vaccine cannot be shed, nor is it infectious.

“It is not biologically possible for the vaccine to do that,” Gunter said.

The false posts weaved together multiple debunked theories, such as period syncing, Gunter noted.

Period syncing is a popular belief that women who are in close proximity to one another can have their periods align.

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“I think this represents a gross misunderstanding of the menstrual cycle. This ties into the myth of period syncing, which is not a thing,” Gunter said. “We don’t give off auras that affect other people’s menstrual cycles.”

Some women have reported a fluctuation in their menstrual cycle after receiving the COVID-19 vaccine, but so far the reports have been anecdotal.

Experts are still determining whether those fluctuations may be linked to stress or immune reactions people have after getting a vaccine.

“When you mount a very robust immune response, that can release hormones that change your menstrual cycle,” said Dr. Andrea L. Cox, professor of medicine at the Johns Hopkins University School of Medicine, noting that the change shouldn’t be long-term.

Either way, irregular periods can’t be spread from person to person. COVID-19 vaccines do not affect fertility or cause miscarriages, data shows.

“Not only do they not cause miscarriages in the people who are near vaccinated people, they do not even cause miscarriages in the people who got them during pregnancy,” Cox said.

Last week, new data was published in the New England Journal of Medicine by researchers at the Centers for Disease Control and Prevention, bolstering evidence COVID-19 vaccines are safe and do not cause miscarriages. The results are based on reports from over 35,000 U.S. women who received either the Moderna or Pfizer shots while pregnant. The rates of miscarriages or premature births were comparable to rates reported before the pandemic.