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A Jackson-Hinds Comprehensive Health Center nurse loads a syringe with a Moderna COVID-19 booster vaccine at an inoculation station next to Jackson State University in Jackson, Miss., Nov. 18, 2022. (AP) A Jackson-Hinds Comprehensive Health Center nurse loads a syringe with a Moderna COVID-19 booster vaccine at an inoculation station next to Jackson State University in Jackson, Miss., Nov. 18, 2022. (AP)

A Jackson-Hinds Comprehensive Health Center nurse loads a syringe with a Moderna COVID-19 booster vaccine at an inoculation station next to Jackson State University in Jackson, Miss., Nov. 18, 2022. (AP)

Madeline Heim
By Madeline Heim June 7, 2023

No, the COVID vaccine has not been proven to have negative efficacy

If Your Time is short

  • The studies Sen. Ron Johnson’s office sent examined COVID vaccine effectiveness, not efficacy. Efficacy refers to how well a vaccine performs in a clinical trial, and each of the vaccines were highly efficacious when they debuted. 

  • Even overlooking that, the claim is off base. The studies do demonstrate waning protection against an omicron infection, but they don’t mean that getting vaccinated caused an increased risk of infection. 

  • What’s more, the goal of the vaccines wasn’t to block infection – it was to prevent severe illness and death, which the same studies show is still happening.

Once he was re-elected for his third term, U.S. Sen. Ron Johnson, R-Wis., said he would put a special focus on what he believes are problems with the COVID vaccines. 

Johnson has long questioned the safety of the shots, pursuing theories that medical experts have said are misinformation.

Johnson was asked about the issue in an April 24, appearance at the Milwaukee Press Club in what became a heated exchange with the WDJT-TV reporter who asked the question. 

After saying he was attacked for claiming that natural immunity from infection would be "stronger" than the vaccine, Johnson threw in a new argument. The vaccine "has been proven to have negative efficacy," he said.

In other words, he’s claiming that instead of offering you protection from COVID-19, the vaccine causes you to be more at risk from the illness. 

Experts say he’s wrong. Let’s take a peek. 

Efficacy versus effectiveness 

When asked for backup, Johnson’s office pointed us to three things: a 2022 presentation from a Centers for Disease Control and Prevention staffer; a 2021 report of coronavirus infections in the United Kingdom; and a 2022 study of vaccinated health care workers at a health system in Cleveland.  

First, a quick lesson on efficacy: The term refers to how well a vaccine performs in a clinical trial. It’s different from effectiveness, which measures how well a vaccine protects a community in the real world. 

Each of the studies Johnson’s office sent measure effectiveness, not efficacy. The vaccines were found to be highly efficacious when they debuted. 

Those trials also set out to see how well the vaccines protected against severe illness and death from COVID-19, not whether they protected against infection, because "the vaccines were never designed with that specific goal in mind," said Ajay Sethi, an epidemiologist and professor at the University of Wisconsin-Madison. 

In other words, the vaccines being efficacious meant they protected well against severe disease and death. 

Assuming Johnson mixed up the terms — easy enough to do — let’s revisit his original statement. Do the shots have negative effectiveness? In other words, if you’re vaccinated, does it make you more likely to get very ill or die from COVID-19? 

Experts say Johnson has misinterpreted studies 

No, experts say. There are a few important caveats to the picture he’s presented. 

First, let’s tackle how much protection the vaccines gave against different variants of the virus. It’s widely acknowledged that the vaccines from early in the pandemic did not protect as well against infections from the omicron variant, which emerged in late 2021, said Patrick Remington, a former CDC epidemiologist and professor emeritus at the University of Wisconsin-Madison. 

The waning protection against an omicron infection as outlined in the CDC chart Johnson’s office sent, then, can best be described by the vaccine not being as close of a match to the new variant, not that being vaccinated caused an increased risk of infection. 

Though the chart does show vaccine effectiveness for an omicron infection dipping below zero, there are problems with the way Johnson’s office interpreted that, Remington said. 

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First, those specific findings were not statistically significant. More broadly, the study was observational research, not a randomized trial, in which the only difference between two groups being studied would have been that one got the vaccine and one didn’t. So, there could be several other variables that led to that dip, Remington said, and it can’t be concluded that the vaccine itself caused it. 

"(In) any observational research study, we have to be cautious when we see a finding that it could be due to chance," Remington said. "That’s why we don’t rely on observational research to make recommendations about vaccines." 

The paper to which the CDC presentation referred also provided evidence that getting a third dose of vaccine was better than stopping at two doses, Sethi said. 

Data included later in the presentation shows that protection against hospitalization and death — the vaccines’ main goal – remained high and was never negative. 

As for the U.K. data, Johnson’s office pointed to a paragraph in the press release that reads, "Those who have received three doses of a vaccine and test positive for COVID-19 are more likely to be infected with infections compatible with the Omicron variant compared with those who are unvaccinated." 

But the rest of that sentence is in itself a dispute of Johnson’s claim: "Individuals who had received at least one dose of a COVID-19 vaccine continued to be less likely to test positive for COVID-19, regardless of variant."

Here again, Johnson conflates waning protection against an omicron infection with the idea that the vaccines are making it more likely that people get infected. 

The final study Johnson’s office presented, of the Cleveland Clinic, examined the effectiveness of the bivalent booster — the one designed specifically to target the omicron variant — and found waning effectiveness as different lineages of the virus emerged. 

Dr. Nabin Shrestha, a staff physician in the Department of Infectious Diseases at the Cleveland Clinic who was an author of the study, said Johnson’s assertion is a mischaracterization of its results. 

"This study found an association," Shrestha wrote. "It did not show that higher doses of vaccine were the cause of increased risk of infection." 

And, again, the study referred to virus infections, not illness and death as the vaccines’ effectiveness was based on. 

Our ruling

Johnson claimed that the COVID-19 vaccines have "been proved to have negative efficacy." 

The studies his office sent as evidence measured vaccine effectiveness, not efficacy, which are two different terms. 

But even a generous interpretation of his statement shows it’s still off base. Although protection against infection waned with the arrival of the omicron variant, the vaccines’ effectiveness was meant to measure how well they protected against severe disease and death, and that level of protection remains robust. 

And even that waning protection doesn’t mean that being vaccinated causes a person to be at higher risk of contracting the virus, experts said. 

We rate this claim False. 



Our Sources

Milwaukee Journal Sentinel, "Ron Johnson's lonely crusade: The re-elected senator vows 'relentless' focus on COVID vaccine injuries widely seen as rare," Feb. 15, 2023

Milwaukee Journal Sentinel, "Facing backlash, Ron Johnson defends news conference with five people who said they got side effects from COVID-19 vaccine," Jan. 17, 2022

Milwaukee Journal Sentinel, "U.S. Sen. Ron Johnson argues with journalist in defending his stance on COVID-19 'vaccine injuries,’" April 24, 2023

Yale Medicine, "What’s the Difference Between COVID-19 Vaccine Efficacy and Effectiveness?" Nov. 5, 2021

Appleton Post-Crescent, "Can I stop wearing a mask once I get the COVID-19 vaccine? Here's what life will be like once you get the shot," Jan. 25, 2021

Email exchange with Ajay Sethi, epidemiologist and professor, University of Wisconsin-Madison 

Email exchange with Patrick Remington, former CDC epidemiologist and professor emeritus, University of Wisconsin-Madison 

JAMA, Association Between 3 Doses of mRNA COVID-19 Vaccine and Symptomatic Infection Caused by the SARS-CoV-2 Omicron and Delta Variants, Jan. 21, 2022

Email exchange with Dr. Nabin Shrestha, staff physician, Cleveland Clinic


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No, the COVID vaccine has not been proven to have negative efficacy

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