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No, Boston University didn’t create a COVID strain with a human mortality rate of 80%

Boston University researchers studied the effects of a lab-made COVID strain on a type of mice that are highly susceptible to the virus.

Researchers at Boston University have come under fire on social media in recent weeks over claims about a lab-made coronavirus strain. 

Some people on social media have claimed that the university made a new strain with an 80% human mortality rate.

“Why are scientists developing a new lethal COVID strain that would kill 80% of people infected? And who would allow them to do that?” one person wrote on Twitter

Several VERIFY readers have also reached out to us with questions about Boston University’s research. Michael asked, “Is it true that Boston University made a COVID strain with an 80% mortality rate?”


Did Boston University create a COVID strain with a human mortality rate of 80%?



This is false.

No, Boston University didn’t create a COVID strain with a human mortality rate of 80%. 

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Researchers at Boston University’s National Emerging Infectious Diseases Laboratories (NEIDL) created a COVID-19 strain that combines the omicron variant’s spike protein with properties of the original coronavirus, and infected mice with the hybrid virus.

According to the preprint study, which has yet to be peer-reviewed, 80% of mice infected with the lab-made strain died.

The strain that the researchers created was actually less dangerous than the original coronavirus strain, which killed 100% of infected mice, the study says. 

NEIDL researchers said the study set out to compare the BA.1 omicron variant with the original coronavirus strain.

Since the omicron variant usually causes less severe disease than prior COVID-19 strains, Boston University researchers were looking into “what part of the virus dictates how serious a disease a person will get,” Ronald B. Corley, NEIDL director and BU Chobanian & Avedisian School of Medicine chair of microbiology, explained. 

Researchers weren’t trying to make a virus that would be more deadly or dangerous to humans, and experts say this strain would not be more deadly. 

More from VERIFY: Claims that Pfizer didn't know if COVID vaccine prevented transmission before rollout are missing context

The misleading social media posts pull a statistic from the preprint study’s abstract published online. 

It says that the lab-made COVID-19 recombinant strain created by BU researchers, which combined the omicron variant’s spike protein with the “backbone” of the original coronavirus strain, inflicted “severe disease with a mortality rate of 80%,” compared to “mild, non-fatal infection” from omicron alone. 

But the posts omit that the 80% mortality rate was in a type of mice that are “highly susceptible” to the virus and this outcome can’t be translated to humans.

“These are numbers you would expect from an animal model that’s been made to be extremely sensitive and easy to be knocked down by coronavirus,” said Derek Lowe, Ph.D., a longtime drug discovery researcher who wrote a commentary piece for his Science Magazine blog on Boston University’s research.

“This does not mean that’s going to happen in humans. It’s definitely not,” Lowe added.

In his blog post, Lowe also noted that early strains of the coronavirus did not lead to a 100% mortality rate in humans, like the original strain did in mice. 

“You build animal models like this to get fast, solid comparisons between mouse experiments, not to take the numbers from them and think that they will directly translate to human disease,” he wrote. 

In a statement provided to VERIFY, Boston University said the research is not “gain-of-function,” as some news headlines have suggested, “meaning it did not amplify the Washington state [original] SARS-COV-2 virus strain or make it more dangerous.”

“In fact, this research made the virus replicate less dangerous,” the university wrote in its statement.

What the study did find is that omicron’s spike protein isn’t responsible for less severe disease associated with the variant, since 80% of mice infected with the lab-made recombinant virus died. 

“It’s not having the omicron spike that makes an omicron virus so much less deadly on this mouse model because it’s still pretty bad,” Lowe said of the study’s findings. 

More from VERIFY: Yes, updated omicron boosters were tested on mice, not humans, before authorization

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