Publications distort misleading analysis of COVID-19 vaccine safety data

An overview of some of the questions asked during a v-safe check-in. Screenshot from a CDC video promoting the v-safe tool.

“It doesn’t have the level of detail and granularity to accurately assess whether these events are causally linked. And you know, there’s no comparison group there, everyone in v -safe is vaccinated, and therefore it is impossible to determine whether a vaccine caused a particular adverse event based solely on the v-safe data,” Belongia told us.

The system is part of a larger early warning reporting system which allows experts to monitor the safety of vaccines. Belongia and other experts say v-safe has limits. But he says the tool has been useful for observing common side effects of vaccines such as pain at the injection site, headache, muscle aches or fever.

“And what we’re seeing is largely consistent with what’s been seen in clinical trials.: this these symptoms are very common, they’re mild to moderate, they resolved in two to three days, so there’s really nothing surprising about that,” he said.

Data collected through v-safe is not publicly available in the same way as data from other systems like the The vaccine adverse event reporting system is. Instead, information is released to the public through several studies that analyze v-safe data in the CDC Morbidity and Weekly Mortality Report and other journals, and in presentations to the Advisory Committee on Immunization Practices. According to the CDC, v-safe data has been presented at 11 meetings since the vaccines were rolled out – in December 2020; January, March, June, September and October 2021; and in January, April, May, June and September 2022.

Some finds of these studies are that the second dose of the primary series caused more participants to report mild, temporary symptoms or being unable to perform normal activity, and that the second booster cause fewer expected side effects, such as pain at the injection site, than the first. According to the CDC, when COVID-19 vaccines began being given, v-safe was essential for identifying early reports a serious allergic reaction which rarely occurs after vaccinations.

A study, published in the Lancet Infectious Diseases in March, analyzed v-safe reports between December 14, 2020 and June 14, 2021, after administration of the Pfizer/BioNTech and Moderna COVID-19 vaccines. According to his findings, Less than 1% of v-safe users reported receiving medical care within the first week after receiving a primary series dose of either vaccine, and a very small proportion (0.2% or less) reported an emergency room visit or hospitalization. Again, even these medical visits are not necessarily caused by the vaccine and could be coincidental.

ICAN’s Misleading Analysis

Informed Consent Action Network is a Texas-based group based by Del Bigtree, a anti-vaccination activist. The group filed several vaccine lawsuits against the CDC, the Food and Drug Administration and the National Institutes of Health. ICAN sued the CDC in December 2021and again in May 2022following FOIA requests for all data submitted to v-safe since January 1, 2020. The v-safe program did not begin until after the COVID-19 vaccines were cleared in December 2020.

In August, the CDC agreed publish data collected from more than 10 million v-safe participants on its website by September 30. The database would cover reports submitted between December 14, 2020 and July 31, 2022 and omit any personal identifiers. The agency said Reuters “technical and administrative” problems prevented it from publishing the data on time. Instead, the CDC transmitted the data directly to ICAN, which published its own analysis on October 3.

On its website, ICAN does not explain the methods used for its analysis. But he mentions that the data is limited to the 10 million v-safe users and the pre-filled fields verified by them, not information that users can add in text boxes. According to the group’s dashboard, the data is drawn from records that occurred up to a year after a vaccine dose. The group too published five downloadable files with raw v-safe data. has contacted Aaron Siri and other Siri & Glimstad representatives, who filed the FOIA dispute for ICAN, but we have not heard back from them. We also tried to access the raw data presented, but we were unable to open the largest file containing information regarding health checks.

We were able to access one of the files containing symptoms and health impacts, which included 116,294 reports. Of these reports, 1,046, or 0.9%, were medical care reports of any kind, and this included multiple reports from the same person over time. Of these, only seven involved hospitalizations, including two for the same person for two consecutive days.

Belongia, the vaccine safety expert, shared with us the figures provided by ICAN, including the more than 780,000 users who have declared that they need medical attention of any kind, are “uninterpretable”.

“We don’t know what the background rate is in the v-safe population. What would that number have been in a group of people who had not received the vaccine? ” he said.

Since health problems, including hospitalizations, occur every day in the population, it is not uncommon for them to arise after vaccination for reasons unrelated to the vaccine. This is why it is important to see if a particular event occurs more frequently after vaccination, which could indicate a problem.

The analysis does not mention how long after vaccination a user needed medical attention, but included responses up to a year after vaccination, which could explain the difference between the ICAN figures and the data published by the CDC. Siri told Reuters that ICAN thinks it’s important to look beyond one week because some potential vaccine-related side effects could show up weeks after vaccination. But most side effects occur shortly after vaccination, so including longer intervals would include more events that are unrelated to the vaccine.

A user may have seen a doctor for a completely different reason six months after a shot and, if they follow v-safe’s instructions correctly, will report this to the system. This user would receive a follow-up call from v-safe, for the agency to get more information. But as we said, v-safe does not have the ability to know whether a particular event, including hospitalization, was caused by the vaccine or not.

“And so to answer questions like that, in terms of relative risk, you need something like the Vaccine Safety DataLink or VSD, which uses the medical records of millions of people across the country and the records vaccination to implement scientifically valid studies to determine if there is an elevated post-vaccination risk for particular adverse events,” Belongia said, referring to a network of nine integrated health organizationsincluding his own, which actively monitors vaccine safety.

“What we are actually seeing in the data is the exact opposite of what is suggested by groups like ICAN – these vaccines are very safe. With, you know, some very few known exceptions,” Belongia said. “But overall, it’s very clear that the benefits of vaccines far outweigh the risks.”

Editor’s Note: The SciCheck COVID-19/Vaccination Project is made possible by a grant from the Robert Wood Johnson Foundation. The foundation has no control over the editorial decisions of, and the opinions 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 reducing the impact of misinformation.


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