Fact Check-COVID vaccines do not ‘shed’ from one person to another and then cause reproductive problems

False claims that the coronavirus vaccines can be passed – or “shed” – from an immunized person to an unvaccinated woman and then somehow affect the woman’s reproductive system are whipping around social media. Top medical experts agree that it is impossible for a person to transmit the vaccines to people they happen to be near and for a woman to experience miscarriage, menstrual cycle changes, and other reproductive problems by being around a vaccinated person.

“This is a conspiracy that has been created to weaken trust in a series of vaccines that have been demonstrated in clinical trials to be safe and effective,” said Dr Christopher Zahn, Vice President for Practice Activities at the American College of Obstetricians and Gynecologists, the leading U.S. organization for medical professionals in women’s healthcare.

Calling the vaccines “our single best tool for confronting a global pandemic that has taken 600,000 lives in this country alone,” Zahn added in a statement emailed to Reuters that “such conspiracies and false narratives are dangerous and have nothing to do with science.”

Posts such as those found here, here , here , here , and here falsely claim that vaccine “shedding” may cause a variety of reproductive problems and that women should avoid associating with vaccinated people.

Many posts also state that receiving vaccine shots can interfere with menstruation, citing anecdotes about women who have been vaccinated. Researchers are currently investigating the anecdotes, and at this time Reuters cannot assess the validity of the claims.

The term “shed” was used frequently in the early days of the pandemic to describe people transmitting or emitting coronavirus particles. Scientists measure “viral shedding” to try to pinpoint at what point sick people are the most infectious ( here ).

“There is no way for a COVID-19 vaccinated person to “shed vaccine,” the Centers for Disease Control’s COVID-19 Clinical Team said in an email responding to Reuters questions.

“COVID-19 vaccines give instructions to teach our cells how to make a protein—or even just a piece of a protein—that triggers an immune response inside our bodies. After the protein piece is made, the cell breaks down the instructions and gets rid of them. The immune response, which produces antibodies, is what protects us from getting infected if the real virus enters our bodies.”

The team also stated the vaccines cannot cause people to shed the COVID-19 virus, echoing all the other experts Reuters spoke to, saying “COVID-19 vaccines do not use the live virus that causes COVID-19 and cannot cause COVID-19. Therefore, people who receive a COVID-19 vaccine cannot shed the virus or the vaccine.”

Many of the false posts attribute the “shedding” of vaccines to a “spike protein” in an apparent misunderstanding of how the vaccines work.

The mRNA vaccines “contain only instructions for making spike protein and are incapable of generating virus particles, so nothing can be shed,” said Dr Daniel Kuritzkes, chief of the infectious diseases division at Brigham and Women’s Hospital, one of the world’s top teaching hospitals and part of Harvard Medical School, in a statement emailed to Reuters.

Likewise, the Johnson & Johnson (also referred to as Janssen) vaccine “is based on a replication-defective adenovirus, which means the adenovirus is incapable of reproducing,” he added.

As Reuters explained here the Pfizer-BioNTech and Moderna COVID-19 vaccines use a chemical messenger, or mRNA, to tell people’s cells to make “make proteins that mimic the outer surface of SARS-CoV-2 (the virus that causes COVID-19)…without replicating like the actual virus.” Meanwhile, the J&J vaccine uses a “weakened version of a harmless adenovirus to deliver instructions to cells to make coronavirus spike proteins” that also cannot replicate, as Reuters reported here .

Kuritzkes also pointed out that the mRNA vaccines are degraded within 24 to 48 hours. As explained here , that means they disappear from the shot recipients’ bodies within a day or two. Similarly, the J&J vaccine “gets taken up into cells where it is injected, makes spike protein, and is degraded. It cannot disseminate to other tissues or be shed,” Kuritzkes said.

The New York Times illustrates in detail how that vaccine works here .

The Food and Drug Administration and Centers for Disease Control and Prevention (CDC) have recommended a pause in the J&J vaccine while they investigate six cases of a rare blood clot in six women who received it ( here ).

Looking at research and data on the coronavirus and vaccinations, the National Institutes of Health have not found vaccine “shedding.” The NIH, the world’s largest biomedical research agency ( ), continues to advise that people remain cautious about the coronavirus itself, even when around vaccinated people. It recommends vaccinated individuals continue to wear masks, practice physical distancing and use other measures to reduce the spread of the virus, given that there are cases of people who have been infected even after being fully vaccinated.

“There is no evidence that individuals vaccinated for COVID-19 can transmit the vaccines to others or that vaccination of one person can have negative health effects on others,” said an NIH spokesperson in a statement emailed to Reuters.

More research is needed to assess the posts claiming that receiving a vaccine shot can disrupt a woman’s period.

The clinical trials for the three vaccines approved for emergency use in the United States did not look into possible issues related to menstruation as seen here, here and here .

A January 2021 study found that COVID-19 infections affected some people’s menstrual volume and cycle length ( here ). But there aren’t any studies to illuminate recent anecdotes on social media about earlier periods, heavier flows and more painful cramps related to vaccinations ( here).

The Vaccine Adverse Event Reporting System managed by the CDC and Food and Drug Administration received reports of menstrual cycle changes.

Kathryn Clancy, a University of Illinois Urbana-Champaign associate professor in anthropology, and a fellow researcher are conducting an on-line survey here about the relationship between COVID-19 vaccines and menstruation that has received thousands of responses ( here ).

Still, Dr Miriam Laufer, Professor of Pediatrics, Medicine, Epidemiology and Public health at the University of Maryland School of Medicine, said “the vaccine does not impact the hormones that are responsible for a woman’s menstrual cycle.”


False. It is impossible to “shed” the coronavirus vaccine. Being around vaccinated people cannot hurt a woman’s reproductive system.

This article was produced by the Reuters Fact Check team. Read more about our work to fact-check social media posts here  .