The only vaccine to have caused any significant number of infections is the oral polio vaccine (OPV) in the 1950s, and this vaccine is no longer used in developed countries.
Vaccine shedding is a term used for the release of virus following administration of a live-virus vaccine. Shedding is a popular anti-vaccination trope, but, with the exception of the oral polio vaccine (OPV) in the 1950s, there have been few documented cases of vaccine-strain virus infecting contacts of a vaccinated person.
Viral shedding is part of the normal mechanism of virus transmission. Shedding is impossible with killed vaccines or those made using only isolated proteins (most vaccines fall into one of these two classes), but a small number of vaccines contain live attenuated virus which can theoretically infect others. Not all pathogens are shed; shedding does not equal transmission; and transmission does not always cause disease.
The only vaccine to have caused any significant number of infections is the oral polio vaccine (OPV) in the 1950s, and this vaccine is no longer used in developed countries. The route of infection was through contact with faeces, and some vaccines, like the viruses they prevent, are shed in stool for up to 28 days. Normal hygiene is sufficient to prevent infection but immunocompromised individuals need to be especially diligent. Other attenuated vaccines show no significant shedding, inadvertent infection is rare (for example, there are eleven cases of chickenpox which may have been transmitted by vaccinated individuals out of approximately fifty million doses), and only a single case of transmission of influenza virus has been documented, and that person remained asymptomatic. The attenuated virus from vaccines is much weaker and less likely to infect than the wild virus.
The Latest Anti-Vax Myth: ‘Vaccine Shedding’
— Miami school cited it as the reason for rejecting vaccinated teachers
by Kristina Fiore, Director of Enterprise & Investigative Reporting,
April 29, 2021
When a Miami school said earlier this week that it wouldn’t allow vaccinated teachers in its classrooms, its founder cited “vaccine shedding” as her main concern.
The trope is currently abuzz in anti-vaccine circles, said Nicole Baldwin, MD, a pediatrician who has been a target of attacks by the anti-vaxxer community.
“It’s amazing, and sad, what people will believe,” Baldwin told MedPage Today.
Essentially, they believe that people who’ve had the vaccine can somehow shed the spike protein, which in turn can cause menstrual cycle irregularities, miscarriages, and sterility in other women just by being in close proximity.
“This is a new low, from the delusional wing of the anti-vaxx cult,” said Zubin Damania, MD, a.k.a. ZDoggMD, in a video he recently posted to bust vaccine shedding myths.
Damania said the misinformation originates from an earlier claim that syncytin, a protein involved in placental formation, bears some structural similarities to the spike protein, and therefore vaccination would interfere with women’s reproductive systems. Many a fact check has shown that vaccines don’t target the protein.
Once injected, the vaccines prompt cells to make the spike protein, but it’s usually cleared in 24 to 48 hours, leaving little opportunity for “shedding,” even if it could occur — which it can’t, Damania emphasized.
Damania noted that there are legitimate questions and research about whether the coronavirus itself and vaccines have an impact on women’s menstrual cycles. Since the beginning of the pandemic, women who’ve had COVID-19 reported changes to their menstrual cycle, and Damania said that researchers are assessing reports of changes to the menstrual cycle following vaccination.
Regarding the potential relationship to vaccination, “we don’t understand, first, if it’s true, and if it were true, what is the mechanism?” he said. “Anything that causes stress, inflammation, and an immune response may have an effect on the menstrual cycle. … Could it be that the vaccine causes a temporary change in menses? Sure, it’s possible, and it’s being looked at.”
Leila Centner, co-founder and CEO of Centner Academy, the Miami school that has banned vaccinated employees, told NBC News in a statement that “tens of thousands of women all over the world” have reported reproductive issues from being around someone who has been vaccinated.
Baldwin pointed out an Instagram video, now marked as misinformation, in which a nurse, Maureen McDonnell, RN, and a physician, Lawrence Palevsky, MD, discuss the effect of vaccines on women’s menstrual cycles.
“This isn’t just a trivial thing,” Damania said. “It’s quite harmful.”Last Updated April 29, 2021
- Kristina Fiore leads MedPage’s enterprise & investigative reporting team. She’s been a medical journalist for more than a decade and her work has been recognized by Barlett & Steele, AHCJ, SABEW, and others. Send story tips to email@example.com. Follow
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.
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 .
Our Standards: The Thomson Reuters Trust Principles.