Danish Study Suggests mRNA-based Vaccines Associated with Greater Overall Mortality

Posted originally on TrialSite News by Staff on April 11, 2022

Recently scientists from Denmark led an important study suggesting that mRNA-based vaccines such as the ones made by Pfizer or Moderna may not be as safe as adenovirus-based vaccines such as Johnson and Johnson, AstraZeneca/Oxford or the one produced by China’s CanSino Biologics. Led by Peter Aaby, a trained physician and anthropologist that runs a health and demographic surveillance system site in West Africa as part of the Bandim Health Project and Dr. Mihai Netea a well-known award winning Romanian/Dutch scientists and Danish colleagues from Odense Patient Data Explorative Network (OPEN) at University of Southern Denmark, the group scrutinized possible “non-specific effects” (NSEs) of the COVID-19 vaccines probing into overall mortality such as not only COVID-19 deaths but also accidental deaths, cardiovascular deaths and other non-COVID-19 deaths. The team discovered that out of 74,193 participants in mRNA clinical trials and 61 deaths, that based on relative risk there was no real difference between the vaccine and placebo group. While in the adenovirus-based studies with 122,164 participants and 46 deaths the vaccine had nearly half the level of deaths as compared to the controls group.

The study team decided to take a step back and look at the COVID-19 vaccine clinical trial data from a different point of view. They did this because “there is now ample evidence that vaccines can have broad heterologous effects on the immune system.” Such effects can either A) greater protection or B) increased susceptibility to unrelated infections or even other non-infectious autoimmune diseases. The authors report that emerging study data reveals that “vaccines may have completely unexpected effects on overall mortality, different from what could be anticipated based on the protection against the vaccine-targeted disease.”

The study results await peer review thus the data shouldn’t be considered evidence. But the novel approach and consequent findings represent an important potential contribution to our scientific knowledge of the COVID-19 vaccines.

Overall Mortality wasn’t Studied

Taking a different perspective, Dr. Aaby and team share that the current batch of COVID-19 vaccines were not tested to evaluate their effects on overall mortality. That would have been difficult given the short follow-up in the studies as subjects participating in the control groups received the vaccine after 3-6 months based on the emergency use authorization situation.

Surprisingly, although all would assume that the COVID-19 vaccines would reduce overall mortality in the pandemic this assumption hasn’t been formally vetted in studies. 

The authors utilized the final study reports available from the COVID-19 vaccine trials investigating the impact of mRNA and adenovirus-vector COVID-19 vaccines on overall mortality, including the previously mentioned other categories such as cardiovascular-related deaths.

The Findings

The table below highlights these study findings:

 ParticipantsDeathsRelative Risk
mRNA74,19361 (mRNA 31; placebo; 30)1.03 (95% CI=0.63-1.71)
Adenovirus122,16446 (vaccine: 16; controls:30)0.37 (0.19-0.70)

Aaby and team report that the adenovirus-vector vaccines were associated with protection against COVID-19 deaths (RR=0.11 (0.02-0.87)) and non-accident, non-COVID-19 deaths (RR=0.38 (0.17-0.88)).

Of note, mRNA-based vaccines differ markedly from adenovirus vaccines regarding impact on overall mortality (p=0.030) as well as non-accident, non-COVID-19 deaths (p=0.046). The placebo-controlled RCTs of COVID-19 vaccines were halted rapidly due to clear effects on COVID-19 infections. Importantly the data derived from this study suggest an important need for randomized controlled trials of mRNA and adeno-vectored vaccines head-to-head comparing long-term effects on overall mortality.

Brief Discussion

Of course, many experts may summarily dismiss such findings as not relevant. After all the COVID-19 studies were designed to determine if the vaccines were effective in protecting against death from SARS-CoV-2, the virus behind COVID-19. Yet the authors point out that “non-specific effects, and their immunological basis, have been established for several other vaccines.”  For example, the authors point to randomized controlled trials showing that BCG vaccine against tuberculosis (TB) lessens neonatal mortality, yet this was because the vaccine protects against deaths from sepsis and respiratory infections.

They point out that “immunological studies have shown that such effects are indeed biologically plausible; BCG positively affects the innate immune system leading to enhanced resistance towards a broad range of pathogens. Furthermore, the BCG vaccine has been associated with decreased systemic inflammation.”


The authors conclude that if their findings are in fact validated by randomized controlled studies then the adenovirus-based vaccines may prove beneficial to their “protective heterologous effects…on non-COVID-19 mortality” as well as their effectiveness against SARS-CoV-2 infection.  Could these vaccines represent an advantage in vulnerable populations susceptible to cardiovascular mortality.  Key is a better understanding of the heterologous effects between the different vaccine types.

Study Funding

Dr. Allen Schapira funded the work on non-specific effects of vaccines while some of the previous work was funded by the Danish Council for Development Research, Ministry of Foreign Affairs, Denmark; Novo Nordisk Foundation and European Union.   

Lead Research/Investigator

Peter Aaby, DMSc, Bandim Health Project, INDEPTH Network; Bandim Health Institute – OPEN, Institute of Clinical Research

Christine Stabell Benn, University of Southern Denmark – Odense Patient Data Explorative Network (OPEN); Bandim Health Project, INDEPTH Network

Frederik Schaltz-Buchholzer, Statens Serums Institut – Bandim Health Project

Sebastian Nielsen, University of Southern Denmark – Odense Patient Data Explorative Network (OPEN)

Mihai G. Netea, Radboud University Nijmegen – Radboud Center for Infectious Diseases (RCI); Radboud University Nijmegen – Department of Internal Medicine


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