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SciCheck’s COVID-19/Vaccination Project

Irish Professor Makes Unfounded Claims About Long-Term Effects of mRNA Vaccines


This article is available in both English and Español

SciCheck Digest

The COVID-19 mRNA vaccines authorized for use were found to be safe and effective in clinical trials and real-world conditions. A professor in Ireland baselessly claims in a video circulating on social media that they are not, and that those who get the vaccines will die as a result within several years.


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Update, Aug. 23: The Pfizer/BioNTech COVID-19 vaccine, which was previously authorized by the Food and Drug Administration for emergency use, received full approval from the agency on Aug. 23 for people 16 years of age and older.

The mRNA vaccines against COVID-19 represent a new vaccine platform, but their development rests on years’ worth of research, including clinical trials. And while the vaccines were developed quickly in response to the pandemic, they have been proven to be safe and effective not only in standard clinical trials but in real-world conditions.

The vaccines in question use modified messenger RNA to provide instructions for cells to make spike proteins that then trigger an immune response against the spike protein of the SARS-CoV-2 virus, which causes COVID-19. The cells quickly break down the mRNA.

But as the vaccines are deployed around the country, some have weaponized their novelty to spread misinformation and unfounded claims about their safety.

In one case, a video clip circulating online shows Dolores Cahill — a professor in Ireland who until recently was the chair of the right-wing Irish Freedom Party — baselessly claiming that COVID-19 mRNA vaccines will cause widespread deaths in the coming years.

Cahill specifically alleges that “anyone who’s over 70 who gets one of these mRNA vaccines will probably be — sadly die within about two to three years.”

“And I would say anyone who gets the mRNA injection, no matter what age you are, your life expectancy will be reduced to you know die, if you’re in your 30s, within five to 10 years,” continues Cahill, a professor at the medical school at the University College Dublin who has previously come under criticism for spreading misinformation about COVID-19.

There is no medical evidence for such claims.

In phase 3 trials, the two mRNA vaccines authorized in the U.S. — from Pfizer/BioNTech and Moderna — had an efficacy of 94% or higher, which means your approximate risk of getting sick is cut by 94% or more if you are fully vaccinated. A Centers for Disease Control and Prevention study released in March found that, in real-world conditions, the two vaccines were 90% effective in preventing infections. (For more, see our SciCheck stories “A Guide to Pfizer/BioNTech’s COVID-19 Vaccine” and “A Guide to Moderna’s COVID-19 Vaccine.”)

The video clip of Cahill has been repeatedly posted and viewed by tens of thousands on platforms such as Instagram, Twitter and Telegram and is branded as coming from a group called the “World Freedom Alliance,” which Cahill helped found in November. In a video announcing the group’s formation, one member referred to COVID-19 as a “hoax”; Cahill said the group would “expose the truth of what’s going on” in order to protect freedoms.

The clip now spreading online is taken from a speaking event in Belfast in March. The full video shows Cahill making a host of other erroneous claims, including that the vaccines “contain nanoparticles and you can be tracked.” The nanoparticles (a unit of size) referenced are actually lipid nanoparticles, material that helps to protect and transport the mRNA to the cell; they are not part of a technology that can track people.

We’ll address some of Cahill’s unsubstantiated claims in the viral clip here.

Unfounded Claim of Future Deaths

It’s unclear what exactly is behind Cahill’s wild and baseless claim that the vaccines will cause all recipients to die within a matter of years. Our inquiries to Cahill went unanswered.

Meanwhile, Grant McFadden, director of the Biodesign Center for Immunotherapy, Vaccines, and Virotherapy at Arizona State University, told us in an email that “the safety record for the mRNA vaccines is excellent.”

McFadden said that while “we do not yet have long-term data in humans,” there “are no scientific reasons to predict complications in these new vaccines in the coming years.” He added that “common health practices mandate that this will be monitored carefully for years to come.”

In a different video uploaded earlier this year, Cahill also predicts widespread deaths specifically from the mRNA vaccines by misrepresenting old studies unrelated to the mRNA technology.

In one case, she cites a 2012 study dealing with vaccine candidates for SARS-CoV (the coronavirus behind the SARS outbreak of 2003).

“What happened in this study is that the animal models after [they] have been challenged got very sick and that some of them died,” Cahill says.

As we noted in a previous story, those vaccine candidates for SARS-CoV were not mRNA vaccines, as Cahill implies. And while the study found that the vaccine candidates being tested caused mice to develop eosinophilia — a high count of a type of white blood cells — when exposed to the live virus, the animals didn’t die, as our fact-checking colleagues at Reuters have explained.

Moreover, that phenomenon, in which a vaccine can lead to worse disease when confronted with a live virus, was not observed in the animal or human trials for the COVID-19 vaccines that received emergency use authorizations.

Cahill in the earlier video similarly references another vaccine trial against respiratory syncytial virus, or RSV. That trial, from the 1960s, also did not involve an mRNA vaccine, as she suggests.

“Most of the children who were given this RSV vaccine, which had the same issue, most of the children experienced severe disease with infection that led to a high frequency of hospitalizations — and two children out of 35 died,” she says. “And the conclusion from this was that the disease was enhanced by the prior vaccination.”

“What people need to know is that with these RNA vaccines is that after you’re vaccinated, for the rest of your life, you will have much higher death as the children did with this study because you were vaccinated,” she adds.

That case actually involved a formalin-inactivated vaccine candidate. Researchers did find that the design of the vaccine candidate resulted in poorly developed antibodies and that the immunized children who still caught RSV suffered worse symptoms than usual. Two children who were part of the trial died as a result of the enhanced disease; the trial stopped and no RSV vaccine has been approved.

But again, this type of phenomenon has not been seen with the COVID-19 vaccines granted emergency use authorization in the U.S.

“Neither COVID-19 disease nor the new COVID-19 vaccines have shown evidence of causing [antibody-dependent enhancement],” the Vaccine Education Center at the Children’s Hospital of Philadelphia reports. “People infected with SARS-CoV-2, the virus that causes COVID-19, have not been likely to develop ADE upon repeat exposure.”

Some scientists who noted the possibility of this issue occurring, as COVID-19 vaccine development was underway, have since said subsequent data helped to quell those concerns.

Dr. Peter Hotez, the dean of Baylor College of Medicine’s National School of Tropical Medicine, said in an email to us that he was among the scientists who flagged the need for researchers “to be on the lookout for immune enhancement” — including in testimony before the House in March 2020 — “based on our work on SARS 1 in rodent models last decade.”

“But as we and others started doing non human primate vaccine trials for SARS 2 it never materialized,” Hotez, also co-director of the Texas Children’s Hospital Center for Vaccine Development, said. “That’s why we do the science.”

Other Baseless Risk Claims

Many vaccine recipients experience pain at the site of injection, fatigue, muscle pain or headache, as we’ve explained. Data from the Pfizer/BioNTech and Moderna trials also show the side effects included joint pain, chills or fever.

A small number of people in the U.S. have had serious allergic reactions following receipt of the shots. That’s why the CDC advises that anyone who has previously experienced anaphylaxis or had any kind of immediate allergic reaction to any vaccine or injection be monitored for a half hour after getting the shot. (The FDA also recommends against vaccination for those who have had a serious allergic reaction to a previous dose of either the Pfizer or Moderna vaccine or one of the ingredients of any of the authorized vaccines.)

In the video clip circulating online, though, Cahill suggests without evidence that recipients will go on to “probably have allergy, neuro-cognitive issues, and inflammation, and of course infertility is the major one.”

We’ve previously addressed the lack of evidence for the claim that the COVID-19 vaccines cause infertility. While clinical trials did not probe the issue, loss of fertility has not been reported among thousands of trial participants and it has not been confirmed as an adverse event among the millions who have been vaccinated.

And as for the other supposed long-term effects, Hotez said “there is zero evidence to support such claims.”

“Also there is not even a plausible mechanism, it’s just antivax gobbledygook,” he said.

While Cahill’s claims about supposed long-term effects of the COVID-19 mRNA vaccines aren’t rooted in evidence, there is support for the fact that COVID-19 itself can result in long-term health effects.

Hotez pointed out that some who contract COVID-19 suffer from what’s known as long-haul COVID and continue to report health issues well after being infected. Among such issues, researchers have found that some such patients continue to experience neurological or psychiatric conditions in the months following infection.

Editor’s note: SciCheck’s COVID-19/Vaccination Project is made possible by a grant from the Robert Wood Johnson Foundation. The foundation has no control over our editorial decisions, and the views expressed in our articles do not necessarily reflect the views of the foundation. The goal of the project is to increase exposure to accurate information about COVID-19 and vaccines, while decreasing the impact of misinformation.

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