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Claim by Mercola that the Pfizer-BioNTech COVID-19 vaccine causes immunosuppression is inaccurate, misrepresents study’s findings

Posted on:  2022-04-21

Key takeaway

COVID-19 is more likely to cause myocarditis as well as other complications as compared to COVID-19 vaccines. Scientific evidence shows that the benefits of the COVID-19 vaccines outweigh their risks. Claims that the vaccines make people more susceptible to COVID-19 are inaccurate and commonly based on flawed analyses and cherry-picked data.

Reviewed content


“Pfizer Knew About Immunosuppression”; “Fully Vaxxed Are More Likely to Die From COVID”

Source: The Epoch Times, Mercola, Joseph Mercola, 2022-04-14

Verdict detail

Factually inaccurate: Contrary to the article’s claim, vaccinated people are less likely to develop severe COVID-19 and die. There is also no evidence demonstrating that vaccinated people are immunosuppressed.
Misleading: While COVID-19 mRNA vaccines are associated with an elevated risk of myocarditis, COVID-19 itself is more likely to cause myocarditis than the vaccines. The real-world evidence we have indicates that antibody-dependent enhancement doesn’t occur with COVID-19 vaccines.

Full Claim

“Pfizer Knew About Immunosuppression”; “Pfizer Documents Show High Rate of Myocarditis”; “Fully Vaxxed Are More Likely to Die From COVID”; “Antibody-Dependent Enhancement Has Not Been Ruled Out”


An article written by Joseph Mercola and republished by The Epoch Times claimed that the “FDA and Pfizer knew COVID shot caused immunosuppression” and that fully vaccinated people are more likely to die from COVID-19. It also claimed that no COVID-19 vaccine has completed Phase 3 clinical trials and suggested that antibody-dependent enhancement remains a concern from COVID-19 vaccines.

Mercola has made many inaccurate and misleading health-related claims, including promoting homeopathy and that COVID-19 deaths “have been vastly overcounted” . Similarly, The Epoch Times has repeatedly published inaccurate and misleading information about COVID-19 vaccines, as previous Health Feedback reviews documented.

Several of the article’s claims hinge on the “Pfizer documents”. These documents were released by the U.S. Food and Drug Administration (FDA) in response to a Freedom of Information Act (FOIA) request by the group Public Health and Medical Professionals for Transparency (PHMPT), filed in September 2021. The group had demanded the data submitted by Pfizer for the approval of the Pfizer-BioNTech COVID-19 vaccine.

Dorit Rubinstein Reiss, a professor of law at the University of California Hastings, discussed the FOIA lawsuit by PHMPT here, explaining how the request was exploited to create “talking points” that promote COVID-19 vaccine doubt and hesitancy.

This is unsurprising. As Reiss noted, the group counts among its members several people who made false claims about vaccines, such as Peter McCullough, Ryan Cole, and Byram Bridle. All three previously made inaccurate or misleading claims about COVID-19 vaccines (see here, here, and here).

This review examines the evidence for Mercola’s claims and explains why the claims are inaccurate and misleading.

Claim 1 (Lacks context): “Pfizer Documents Show High Rate of Myocarditis”

Public health authorities like the U.S. Center for Disease Control and Prevention (CDC) have acknowledged that myocarditis, an inflammation of the heart muscle, is a risk associated with COVID-19 mRNA vaccination.

But what Mercola’s article didn’t tell readers is that COVID-19 itself is more likely to cause myocarditis, as well as other heart complications, compared to the COVID-19 vaccines. A CDC report from 1 April 2022[1], which compared the risk of heart complications—including myocarditis and pericarditis—after COVID-19 vaccination or COVID-19, found that the risk of heart complications was two to six times higher post-infection than post-vaccination, and seven to eight times higher among men aged between 18 to 29 years old.

Furthermore, post-vaccination myocarditis tends to be milder than post-infection myocarditis. Overall, the benefits from the COVID-19 vaccines outweigh their risks. The American College of Cardiology stated that:

The clinical course of VAM [vaccine-associated myocarditis] is generally mild, with most symptoms resolving prior to hospital discharge. Even in the adolescent male population, the entirety of the protective effect of COVID vaccination, particularly in preventing severe COVID, hospitalization, MIS-C, and death, continues to clearly exceed the risk of VAM.

Claim 2 (Inaccurate and Misleading): “Pfizer Knew About Immunosuppression”

For this claim, the article cited a study published in August 2020[2], included among the documents released by Pfizer. That study reported the results of a Phase 1/2 trial of the Pfizer-BioNTech COVID-19 vaccines in adults.

While the study did report “transient decreases in lymphocytes”, the article exaggerated this result, claiming that this was indicative of immunosuppression. Immunosuppression occurs when the immune system no longer functions well enough to fight disease-causing microorganisms and other diseases. This can be the result of disease or medication, such as those taken by organ recipients to prevent organ rejection.

However, the study stated that the decrease was “not associated with clinical findings”—that is, the researchers didn’t observe overall changes in the participants’ health associated with the decrease.

The study also explained that “RNA vaccines are known to induce type-I interferon, which has been associated with transient migration of lymphocytes into tissues”. This suggests that the decrease in lymphocytes observed in the blood of study participants could be because the lymphocytes in the blood moved into tissues, not because the participants ended up with fewer lymphocytes in the body after vaccination. Furthermore, the study reported that lymphocyte level returned to normal in all participants after about a week. The study also didn’t report a higher incidence of infection in participants.

Overall, the claim is inaccurate and misleading, as it omitted key information from the study and misrepresented the study’s findings.

Claim 3 (Inaccurate and Misleading): “Fully Vaxxed Are More Likely to Die From COVID”

To support this claim, the article cited The Daily Expose, another outlet that has repeatedly published false and misleading information about the COVID-19 pandemic. In brief, the Daily Expose claimed that the weekly surveillance report from the UK Health Security Agency (UKHSA) for week 13 in 2022 showed greater rates of infection, hospitalization, and death in vaccinated people compared to unvaccinated people.

However, its claim is based on an incorrect formula for calculating vaccine effectiveness. It’s worth noting that this isn’t the first time that the Daily Expose committed this error; a Health Feedback review already pointed out the same error previously.

The U.S. Centers for Disease Control and Prevention (CDC) explains that vaccine effectiveness calculates “the risk of disease among vaccinated and unvaccinated persons and [determines] the percentage reduction in risk of disease among vaccinated persons relative to unvaccinated persons”.

As for how to interpret vaccine effectiveness:

Vaccine efficacy/effectiveness [VE] is interpreted as the proportionate reduction in disease among the vaccinated group. So a VE of 90% indicates a 90% reduction in disease occurrence among the vaccinated group, or a 90% reduction from the number of cases you would expect if they have not been vaccinated.

However, the Daily Expose’s calculations don’t account for caveats that the UKHSA report warned about:

We present data on COVID-19 cases, hospitalisations and deaths by vaccination status. This raw data should not be used to estimate vaccine effectiveness as the data does not take into account inherent biases present such as differences in risk, behaviour and testing in the vaccinated and unvaccinated populations.

The UKHSA report also directed readers to this blog post, which explains why crude comparisons using rates of cases, hospitalization, and deaths based on vaccination status don’t accurately represent vaccine effectiveness:

If we look at the numbers of cases in vaccinated compared to unvaccinated people, the rate of cases in the vaccinated people appears higher for many age groups. This is because there are key differences in the characteristics and behaviour of individuals who are vaccinated compared to those who are unvaccinated. The rates therefore reflect this population’s behaviour and exposure to COVID-19, not how well the vaccines work.

For instance, one factor that the Daily Expose’s calculation didn’t account for is the fact that the number of cases recorded in the fully vaccinated and unvaccinated groups may not be the actual number of cases in each group. This is because one group may tend to exhibit different health seeking behavior compared to the other. This is a potential source of bias when determining vaccine effectiveness.

For example, one group may be more likely to get tested for COVID-19 compared to the other. Thus, the disease would be detected at a higher rate in one group compared to the other, even though the number of actual cases may not necessarily be higher than in the other group.

In addition, the risk of infection in both groups can also differ for reasons that are unrelated to vaccine effectiveness. For instance, people’s behavior following vaccination may change, which alters their level of exposure to the virus. This survey, conducted by the U.K. Office of National Statistics in February 2021, found that those aged 80 and above increased socializing following COVID-19 vaccination.

Contrary to the claims by Mercola and The Daily Expose, multiple studies that account for such factors found that vaccinated people are less likely to develop COVID-19 and die[3-5].

Claim 4 (Misleading): Antibody-dependent enhancement remains a concern with COVID-19 vaccines

Antibody-dependent enhancement (ADE) is a phenomenon in which preexisting antibodies to a pathogen, arising as a result of previous infection or vaccination, lead to more severe disease.

ADE was indeed a concern among scientists during the early stages of COVID-19 vaccine development, as documented in a PNAS article published in March 2020. And the phenomenon was observed with other vaccines, such as a vaccine candidate for the respiratory syncytial virus.

However, scientists have since gathered much more evidence, indicating that COVID-19 vaccines don’t cause ADE. As explained above, a key feature of ADE is more severe disease in people with antibodies than in people without. However, in the real world, vaccinated people are actually less likely to develop severe COVID-19 compared to unvaccinated people. If ADE was occurring in the real world, we would expect the reverse instead.

In other words, while ADE was a theoretical risk in the beginning of COVID-19 vaccine development, there’s plenty of evidence indicating that in the real world, it doesn’t occur with the COVID-19 vaccines. The article’s revival of this concern, which was present very early on in COVID-19 vaccine development but is no longer substantiated by real-world evidence, is misleading.

Correction (28 April 2022):

Professor Reiss’ affiliation was incorrectly stated to be the University of California Los Angeles. It should be the University of California Hastings. We have corrected this error.


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