Incorrect claim that COVID-19 vaccines caused a 143,233% surge in cancer results from flawed calculations that misuse adverse event reporting data
Safety data and multiple studies show that COVID-19 vaccines effectively reduce the risk of severe or fatal COVID-19 cases, while the risk of serious side effects from vaccination is very small. But COVID-19 vaccines come with tighter reporting requirements than earlier vaccines, which results in more adverse event reports to vaccine safety databases compared to other vaccines. This doesn't indicate any safety issues but instead reflects an increased reporting rate.
Inadequate support: No reliable scientific study shows an association between COVID-19 vaccines and cancer. VAERS reports record any adverse events occurring following vaccination, regardless of whether the vaccine caused the event. Therefore, cancer-related reports to VAERS alone can’t demonstrate that COVID-19 vaccines cause cancer.
Misleading: Reporting requirements for COVID-19 vaccines are more stringent than for earlier vaccines, so simply comparing the number of reports for COVID-19 vaccines and flu vaccines can lead to erroneous conclusions.
An Instagram post published in January 2024 claimed that “official data” from the U.S. Centers for Disease Control and Prevention (CDC) showed a “143,233% surge in fatal cancers among Vaxxed Americans”.
The figure most likely originated from an article published on The Exposé on 8 December 2023 titled, “U.S. Government Data Reveals a Staggering 143,233% Surge in Fatal Cancer Cases”. The article explicitly attributed this increase to “the experimental Covid-19 injections”.
The Exposé is an outlet created in the first year of the COVID-19 pandemic that has since published misinformation and conspiracy theories, often based on distorted or misinterpreted data. The article discussed here is another example of such.
Contrary to what the headline and the Instagram post might suggest, the 143,233% figure doesn’t come from an official report from the CDC or other public health agency. Instead, it was calculated by The Exposé based on data from the U.S. Vaccine Adverse Event Reporting System (VAERS).
In this review, we will show that these calculations are incorrect and misleading in multiple ways and don’t support the claim that COVID-19 vaccines cause or increase the risk of cancer. This claim is also inconsistent with published studies showing that people who received a COVID-19 vaccine aren’t more likely to develop cancer compared to unvaccinated people.
VAERS reports alone can’t demonstrate that a vaccine caused or contributed to an adverse event
The Exposé based its calculations on the number of cancer-related adverse events reported to VAERS after COVID-19 vaccination and after vaccination with the flu vaccines. Between December 2020 and August 2022, VAERS registered a total of 2,579 cancer-related adverse events following COVID-19 vaccination. The number of reports for flu vaccines was 64 between 2008 and 2020.
The article didn’t specify whether the search for “cancer-related” adverse events included all events or only fatal, life-threatening and/or serious adverse events.
Considering the total number of COVID-19 and flu vaccine doses administered in the U.S. during those periods, The Exposé calculated the rate of cancer-related reports per 100,000 doses administered. The result was 0.43 for COVID-19 vaccines (2,579 reports x 100,000 divided by 606 million doses administered) and 0.0003 for flu vaccines (64 reports x 100,000 divided by 1,720,400,000 doses administered).
The article claimed that the higher reporting rate following COVID-19 vaccination compared to flu vaccination was evidence that COVID-19 vaccines caused cancer, whereas flu vaccines didn’t. Specifically, the article calculated that COVID-19 vaccination was 1,433 times (0.43/0.0003) or 143,233% (0.0003×100/0.43) “more likely to cause cancer” than flu vaccination. But this isn’t true.
The first hint that these figures are unreliable lies in the fact that The Exposé made a mathematical error in calculating the rate of cancer reports per 100,000 flu vaccine doses. The result should be 0.003, not 0.0003 as the article claimed. This means that the alleged increase in cancer reporting is actually ten times lower than claimed: 143 times (or 14,323%) instead of 1,433 times (or 143,233%).
And the second and most important is that VAERS reports alone are inadequate to establish associations between a vaccine (in this case, the COVID-19 vaccine) and a health problem (in this case, cancer), although they can provide useful signals for further investigation that may establish a causal association. Therefore, the entire reasoning behind the calculations is flawed and doesn’t support the claim.
VAERS is a national vaccine surveillance system co-managed by the U.S. CDC and the Food and Drug Administration. VAERS collects reports on any adverse events that occurred following vaccination, regardless of what caused them. This system is useful for rapidly detecting unusual patterns of adverse events that might be early signs of a safety problem with a vaccine. However, VAERS reports alone can’t determine whether a vaccine caused an adverse event.
Furthermore, anyone can submit a report to VAERS, which means the database may also contain information that is “incomplete, inaccurate, coincidental, or unverifiable”.
A disclaimer on the site notifies users about these limitations, clearly stating:
“The number of reports alone cannot be interpreted as evidence of a causal association between a vaccine and an adverse event, or as evidence about the existence, severity, frequency, or rates of problems associated with vaccines.”
In brief, The Exposé’s calculations are based on a misuse of VAERS reports, and therefore don’t provide any reliable evidence of a link between COVID-19 vaccines and cancer.
VAERS reporting requirements for COVID-19 vaccines differ from previous vaccines; comparisons can be misleading
COVID-19 vaccines require stricter VAERS reporting compared to earlier vaccines, as Health Feedback explained in multiple reviews. Simply comparing the number of VAERS reports for different vaccines doesn’t take into account these differences and can therefore be highly misleading.
In the case of COVID-19 vaccines, healthcare providers are required by law to report all serious adverse events that occur following vaccination “regardless of causality”. These include death, life-threatening adverse events, hospitalization, congenital anomalies, heart inflammation, multisystem inflammatory syndrome, serious COVID-19 cases, and any other important medical event “that may require medical or surgical intervention”. Cancer-related events likely fall within these categories.
In contrast, for flu vaccines healthcare providers are only required to report certain adverse events. These include anaphylaxis, shoulder injury related to vaccine administration, vasovagal syncope, Guillain-Barré Syndrome, and events described as contraindications in the manufacturer’s package insert. In general, only those serious adverse events, including deaths, that are linked to known side effects of the vaccine require reporting. It is doubtful that any flu vaccine lists cancer as a side effect.
In other words, while cancer and cancer-related adverse events that occur after COVID-19 vaccination must be reported to VAERS, reporting these events after flu vaccination is voluntary. Therefore, the higher rate of cancer-related reports following COVID-19 vaccination compared to flu vaccination most likely reflects differences in reporting rather than an actual increase in cancer rates among people who received a COVID-19 vaccine.
No evidence suggests a link between COVID-19 vaccines and cancer
Determining whether a vaccine is causally associated with an adverse event requires an investigation that goes far beyond the number of VAERS reports. One critical step is to assess whether the vaccine is a plausible cause for the observed event. This isn’t the case with COVID-19 vaccines and cancer.
As we explained above, The Exposé didn’t clarify whether the VAERS search for “cancer-related” adverse events involved new diagnoses, deaths, or other types of adverse events. Yet, the headline mentioned “fatal cancers”, conveying the message that at least some of these events were indeed fatal. However, this message is at odds with available scientific evidence.
The 2024 report by the American Cancer Society on cancer trends shows that, while some common cancers have been on the rise for the last three decades, the risk of dying from cancer has actually declined. This trend continued through 2021, which is inconsistent with COVID-19 vaccines leading to cancer deaths.
Published studies also show that people vaccinated against COVID-19 aren’t more likely to die from any cause compared to unvaccinated people[2,3].
After being extensively studied, no reliable evidence suggests that COVID-19 vaccines cause or increase cancer risk. Claims stating otherwise are usually founded on misinterpreted data and have no basis in fact.
The American Cancer Society and the U.S. National Cancer Institute state that no evidence suggests that COVID-19 vaccines cause or make the cancer grow or recur. In fact, cancer patients are at a high risk for severe complications from COVID-19. Therefore, both institutions recommend that people with cancer and cancer survivors, as well as caregivers and close contacts, get the COVID-19 vaccine.
- 1 – Siegel et al. (2024) Cancer statistics, 2024. CA. A Cancer Journal for Clinicians.
- 2 – Bilinski et al. (2023) COVID-19 and Excess All-Cause Mortality in the US and 20 Comparison Countries, June 2021-March 2022. JAMA Network.
- 3 – Xu et al. (2021) COVID-19 Vaccination and Non–COVID-19 Mortality Risk — Seven Integrated Health Care Organizations, United States, December 14, 2020–July 31, 2021. Morbidity and Mortality Weekly Report.