The mRNA COVID-19 vaccines teach the immune system to recognize and fight the coronavirus, greatly reducing the likelihood of severe disease if a person is infected. There is no evidence the vaccines impair immunity, as some, including Fox News’ Tucker Carlson, have baselessly claimed.
How safe are the vaccines?
The two messenger RNA, or mRNA, COVID-19 vaccines from Pfizer/BioNTech and Moderna work by priming the immune system so it can to a coronavirus infection. Large, randomized controlled trials and a substantial body of real-world data support the effectiveness and safety of the vaccines, which continue to provide strong protection against serious illness and death, especially after one or two booster doses.
Conservative television host Tucker Carlson, however, argued that the vaccines might be harming the immune system. On his July 21 on Fox News, he used dubious sources and cherry-picked and misrepresented data to incorrectly conclude that “it’s looking likely that the vaccine might suppress the immune system.” His comments were also on social media.
“Is it possible that the vaccine actually can hurt you, especially if you keep getting boosted? Can it weaken your immune system? Well, that looks possible,” he said, citing the journal Food and Chemical Toxicology, which he said “published the findings of several mRNA researchers, and we’re quoting, ‘In this paper, we present evidence that vaccination induces a profound impairment in type one interferon signaling, which has diverse adverse consequences to human health.’”
Carlson went on to wonder why the press hadn’t covered the paper, which he quoted from again.
“In fact, it’s looking likely that the vaccine might suppress the immune system,” he said. “This fact, the authors concluded, will ‘have a wide range of consequences, not the least of which include the reactivation of latent viral infections and the reduced ability to effectively combat future infections.’”
Carlson then falsely claimed that a study in the prestigious British journal the Lancet made “similar findings.”
Virtually none of what Carlson said was accurate, however. It’s not “fact” that the vaccines suppress the immune system, nor is there any reliable evidence to suggest that it could be true. The paper that Carlson cites, which was written by some individuals opposed to COVID-19 vaccination, misrepresents and distorts other scientists’ findings to make illogical and unfounded claims.
The lead author of the Lancet paper similarly told us that his work, which Carlson misrepresented, “does not show any” of what Carlson alleged.
Unreliable Food and Chemical Toxicology Paper
Carlson’s primary evidence for the vaccines harming the immune system is a much-criticized Food and Chemical Toxicology written by several individuals known for being opposed to vaccination or for spreading health misinformation.
Lead author is a computer scientist at the Massachusetts Institute of Technology who has falsely that vaccines cause autism and has pushed a theory the herbicide glyphosate to COVID-19, unfounded scientific views. Senior author Dr. Peter McCullough is an internist who has spread misinformation about COVID-19 treatments and the vaccines. Another author, , practices naturopathy, a form of alternative medicine that has pseudoscientific methods.
When the paper was first published in April, , with some . (That effort was . Notably, the paper appeared in the journal after the editor-in-chief put a for papers “on potential toxic effects of COVID-19 vaccines.”)
The , which does not present any original research, is a review coupled with an analysis of data from the Vaccine Adverse Event Reporting System, the United States’ early warning system to detect possible safety problems with vaccines. VAERS reports can be submitted by anyone, are not vetted for accuracy, nor do they mean that a reported symptom was necessarily caused by the vaccine; the data have often been mined to incorrectly claim vaccines are dangerous.
Some parts of the literature review are correct, but the conclusions the authors draw about immune function following vaccination are unfounded, experts told us — and the VAERS analysis is flawed, as , a biostatistician at the University of Pennsylvania, has explained on and on his .
“This long review article presents many details about various biological pathways, but their links to mRNA vaccines are almost wholly speculative. In some cases, they link to other vaccines, old mRNA technology, or COVID-19 infection, but are not directly linked to mRNA vaccines,” Morris .
“In fact, so much of their evidence is from papers on severe COVID-19 infections, not vaccination, much content in this article might be better suited to a paper pointing out potential downstream dangers of severe COVID infections rather than raising alarm about mRNA vaccination,” he added.
One of the paper’s core claims is that the mRNA COVID-19 vaccines suppress the innate immune system, specifically the type I interferon response. Interferons are antiviral proteins that of a viral infection, although they also can lead to harmful inflammation. This is the supposed basis the authors use — and Carlson cites — to claim that the vaccines would make it harder to respond to infections and increase the risk of cancer.
But experts who study the interferon response say that’s bogus.
“I am not aware of any report that demonstrates what [is] claimed in the review,” , an immunologist at Boston Children’s Hospital who has the interferon response in patients infected with the coronavirus, told us in an email.
It “doesn’t make any sense with what we know about the vaccine and how it works, and neither it makes sense to what we know about how the immune system works,” he added.
, a molecular biologist at the University of California San Diego who studies interferon and has its role with COVID-19, agreed.
“The authors make some connections to speculate on a possibility, but there is no data or scientific evidence supporting the statement that interferon signaling is suppressed in vaccinated individuals,” she told us in a phone interview.
In fact, Zanoni said, available evidence contradicts the notion that vaccination reduces a person’s ability to mount an interferon response. One , he said, reported that people who had received one dose of the Pfizer/BioNTech vaccine prior to being hospitalized for COVID-19 had a better antiviral interferon response than those who were not vaccinated.
Another also argues against the idea, Zanoni said. An Italian lab early in the pandemic that a subset of people who develop severe COVID-19 produce antibodies that block their own interferons. These antibodies prevent the interferons from helping fight the coronavirus early in infection, and likely explain the severe disease. The same lab has since that the same applies to vaccinated people — and that individuals with the interferon autoantibodies are likely to be at higher risk of severe illness, even after vaccination.
If the vaccines were suppressing the interferon response, as the review proposes, vaccinated people with autoantibodies would not be at higher risk because interferons would already be suppressed, Zanoni said.
To make its claim that the vaccines suppress interferon, the Food and Chemical Toxicology review cites an that found a much larger interferon response in certain immune cells from people with active coronavirus infections compared with those from people before and after vaccination.
But an author of the study told us that’s an incorrect interpretation of the findings.
“We observed higher levels of interferon signaling in cells from patients with COVID-19 illness than in adults receiving the mRNA vaccines. The paper citing our work is misinterpreting the lack of inflammation to be the same as ‘active suppression,’” , the senior author of the study and an at the New York University Grossman School of Medicine, told us in an email. He added that his group “did not see anything in our data that implies active suppression.”
“We saw very low levels of inflammation in the immune cells following mRNA vaccine in contrast to the high levels that we saw with SARS-CoV-2 virus infection,” he said. “The main message of our manuscript is that even in the absence of inflammation found in the course of infection, vaccination elicits a robust and long-lasting immune response.”
Indeed, less inflammation in the context of a vaccine is part of the point — a vaccine is supposed to provide immunity without the harmful effects of infection.
“This is not surprising at all and there’s nothing wrong with that,” Zúñiga said of the lower interferon response following vaccination.
She also iterated that the finding in no way suggested that the vaccines would diminish the immune system’s interferon response to other pathogens.
Misrepresented Lancet Study
In an effort to lend credibility to his argument, Carlson also claimed that a supported the conclusions of the Food and Chemical Toxicology paper. Except that’s not right, either.
The Lancet paper recommended third-dose COVID-19 vaccine boosters.
Carlson cited a a Japanese physician, Dr. Kenji Yamamoto, published in a different journal, which claimed the Lancet paper “showed that immune function among vaccinated individuals 8 months after the administration of two doses of COVID-19 vaccine was lower than that among the unvaccinated individuals.”
After suggesting that the Lancet paper hid “a major finding,” Carlson pointed to one piece of data in table 3 of the paper for viewers to check themselves. “Among people around the age of 80 who have been double vaccinated — that would include people like Joe Biden — the per capita rate of medical incidences, including hospitalizations or death, is nearly twice as high as the rate of serious incidence for the unvaccinated,” he said.
Carlson added that the Lancet paper “also includes a chart showing negative vaccine efficacy for all ages after eight months for all participants in the study.”
Carlson, however, is distorting cherry-picked data from the paper.
“The paper we have published [does] not show any of the claims” Carlson made, lead author Dr. told us in an email, because they were not statistically significant. The findings that are statistically significant and the conclusions of the paper are “presented in the summary of the paper,” he added.
The paper, which was published in February, used nationwide registers in Sweden to evaluate COVID-19 vaccine effectiveness against infection, hospitalization and death for up to nine months after full vaccination, from December 2020 to October 2021. It found that vaccine effectiveness against infection of any severity waned over time, with some differences by vaccine type (Sweden used the two mRNA vaccines and the AstraZeneca vaccine). There was less waning of vaccine protection against severe COVID-19 — but still some after four months, which the authors said strengthened the rationale for implementing booster doses.
, chair of biostatistics and epidemiology at the London School of Hygiene and Tropical Medicine, told us Carlson’s interpretation of table 3 was “hopelessly wrong and misleading.”
It’s true that for the 80 years and above age group after about six or more months, vaccinated people had nearly twice the incidence of coronavirus infection of any severity as the unvaccinated (1.8 vs. 1.0 per 100,000 person days). However, that’s the raw data — and again, it’s for infection of any severity, not just hospitalizations or deaths, as Carlson suggested.
When the data are adjusted for age and time elapsed since vaccination, Jewell noted in an email, “the data shows the vaccinated individuals in this group to be very slightly better off than the unvaccinated” (a vaccine effectiveness of 4%, rising to 5% with additional adjustments).
The vaccine effectiveness numbers are not statistically significant, so they’re very uncertain. In reality, Jewell said, we “simply don’t know what the effectiveness is for this age group on this time scale since vaccination,” although the evidence “still points to vaccinated individuals being protected from the negative outcome.”
Not only is it inaccurate to conclude from this data that the vaccinated are at higher risk than the unvaccinated, but Carlson also cherry-picked the data. As Jewell noted, the unadjusted data he highlighted is the only such data in the table that shows a higher raw infection frequency among the vaccinated.
“In the other 36 rows,” he said, which show vaccine effectiveness estimates at different times since vaccination for various demographic groups, the vaccinated are the same or better off, sometimes “much better off and definitively so!”
Carlson’s interpretation of figure 2 of the paper, which plots the decline of vaccine effectiveness against infection of any severity over time, is also “completely wrong,” Jewell said. That’s because there is considerable uncertainty in the data, shown by the shaded area, which always includes zero.
“These shaded areas tell us that we have no evidence for effectiveness after 8 months,” Jewell said. “What the figure similarly does not show is that there is evidence of negative vaccine efficacy.”
As for the Japanese physician who claimed the Lancet data “showed that immune function among vaccinated individuals 8 months after the administration of two doses of COVID-19 vaccine was lower than that among the unvaccinated individuals,” Jewell said he found nothing to support that in the Lancet paper, as it also appears to be an erroneous interpretation of figure 2.
Yamamoto’s comment shows a misunderstanding of the figure, and it also incorrectly generalizes a specific and expected decline in immunity to the coronavirus over time following vaccination with a general decline in immunity to all things. There is no evidence of that in the Lancet paper, nor anywhere else.
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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