Fact-checking claims about Danish preprint study on COVID-19 vaccines and mortality

A Danish study that evaluated how the COVID-19 vaccines impact mortality is being used online as evidence that the messenger RNA-based vaccines from Pfizer-BioNTech and Moderna offer "no mortality benefit" at all. 

"mRNA Vaccines Show No Mortality Benefit - Danish Study" is the title of a YouTube video that says the April 5 study found that the mRNA shots from Pfizer-BioNTech and Moderna do not stop infections or transmission and don’t reduce deaths, thus showing "no discernible mortality benefit."

The video adds that, by contrast, the adenovirus vector vaccines from Johnson & Johnson and AstraZeneca do show a "very positive mortality benefit from COVID and, intriguingly, even from non-COVID deaths."

The video features Chris Martenson, a former pharmaceutical financial analyst and founder of Peak Prosperity, a website that appears to be devoted to sharing concepts from a book he authored. It was flagged as part of Facebook’s efforts to combat false news and misinformation on its News Feed. (Read more about our partnership with Facebook.)

PolitiFact reached out to Peak Prosperity for comment but did not hear back.

The study, titled "Randomised Clinical Trials of COVID-19 Vaccines: Do Adenovirus-Vector Vaccines Have Beneficial Non-Specific Effects?" was posted April 5 in the Lancet journal’s preprint server. A "preprint" is a research paper before it is peer-reviewed or accepted for publication by a scholarly or scientific journal. The study was conducted by researchers affiliated with various institutions, including the University of Southern Denmark, the Statens Serums Institut and the Bandim Health Project. 

The research analyzed randomized controlled trials to see how much the COVID-19 vaccines reduced deaths from all causes, and it sought to compare how the results differed between the adenovirus-vector vaccines and mRNA-based vaccines. 

For the mRNA vaccines, the study found that 61 people out of 74,193 participants died. Thirty-one received the vaccine, while 30 received a placebo, thus showing that the vaccine essentially had no impact on "overall" mortality, according to the study.

For the adenovirus-vector vaccines, the study recorded 46 deaths out of 122,164 participants. Of the 46, 16 had received the vaccine, while 30 received a placebo. 

The authors concluded that the two types of vaccines differed significantly "with respect to overall mortality." They also said that adenovirus vaccines were associated with protection against non-accident, non-COVID-19 deaths.

But when looking at COVID-19 mortality rates specifically, the picture changes. 

The study found that of the 31 deaths that occured in mRNA-vaccinated individuals, only two were from COVID-19. The rest were due to other causes. For the adenovirus-vaccinated group, two of the 16 deaths were from COVID-19.

One of the study’s lead authors, Dr. Christine Stabell Benn, a professor of global health at the University of Southern Denmark, made a post about the findings on her LinkedIn page. She argued that scientists cannot presume to know the full effect of a vaccine "just by knowing its effect against the target infection" and said scientists need to study its effect on overall health.

"We need to be clear about which vaccine, and what outcomes, we are talking about," Benn wrote. "The analysis of the randomized clinical trials suggests that COVID-19 vaccines are not a homogeneous group. Hence, we (health authorities, medical doctors, politicians, media as well as citizens) need to distinguish between ‘mRNA COVID-19 vaccines’ and ‘adenovirus vector COVID-19 vaccines’, and we need to specify if we talk about COVID-19-specific mortality or all-cause mortality."

She wrote that headlines that say COVID-19 vaccines reduce mortality are too simplified. 

But the same argument can be said for the YouTube video’s title — that mRNA vaccines offer "no mortality benefit." It’s misleading because it doesn’t specify that the findings are about non-COVID-19 related deaths, that the study is a preprint, or that more research is needed. While scientists like Benn contend that it’s important to study overall mortality effects of vaccines, people received these shots to protect themselves against COVID-19, which these vaccines continue to do. 

"The study isn’t about the effectiveness of mRNA vaccines against COVID," said Amesh Adalja, a senior scholar at the Johns Hopkins Center for Health and Security. "The study is aimed to determine if COVID vaccines have non-specific mortality impacts that extend beyond the incontrovertible mortality benefit they confer with COVID-19. Certain vaccines have effects that extend beyond the target infection and decrease mortality from other causes (e.g. measles vaccine)."

Dr. Monica Gandhi, an infectious disease specialist at the University of California, San Francisco, also said the question of the paper isn’t about COVID-19, but whether the vaccines had a beneficial effect on other causes of mortality.

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The research reinforced that both types of vaccines significantly prevented COVID-19 deaths, "which is not surprising as both types of vaccines generate cellular immunity against SARS-CoV-2, protecting us against severe disease."

The study’s results showing a stronger association between improved mortality and the adenoviral-vector vaccines could suggest these vaccines have other beneficial effects, Ghandi said. But, again, that does not mean there is no mortality benefit to the mRNA vaccine.

"However, to be fair," Gandhi said, "the number of non-COVID and COVID deaths were rare in all of the pooled analyses and the causes of non-COVID deaths not well adjudicated, so this analysis needs to be taken as preliminary and hypothesis generating at best."

The authors acknowledged that the study was based on limited available data over a shorter than desired timeframe.

In an email to PolitiFact, Benn said she feels the lack of data documenting whether the vaccines reduce deaths from causes other than COVID-19 is an area in need of additional research and suggested such data can give a fuller picture of overall vaccine safety. 

Meanwhile, in an emailed statement, Pfizer said that numerous peer-reviewed studies around the world have confirmed the safety and efficacy of its COVID-19 vaccine.

"With hundreds of millions of doses administered globally, the benefit risk profile of our vaccine remains positive for all approved indications and age groups and we remain confident in the protection and safety our COVID-19 vaccine provides," the statement read. 

A video circulating on social media claims that a Danish study found that mRNA vaccines offer "no mortality benefit."

This is an oversimplification that doesn’t accurately reflect the preprint study, which was not peer reviewed. Researchers used clinical trial data to see how the different COVID-19 vaccines reduced deaths from all causes. They found that adenovirus-vector vaccines appeared to protect against non-accident, non-COVID-19 deaths, while mRNA vaccines didn’t have much of an impact. They said more research is needed. 

The research didn’t conclude that mRNA vaccines were ineffective at protecting people from dying of COVID-19. 

We rate this False.