Health experts are now voicing concern over the possibility of another pandemic after researchers at Boston University created a COVID-19 strain with an 80% kill rate.

A team of scientists from Florida and Boston at the university's National Emerging Infectious Diseases Laboratories combined the spike protein from the BA.1 Omicron variant with the original virus in Wuhan. The new lab-created strain was tested on a group of mice, 80% of which died. In contrast, a group of rodents exposed to the standard Omicron strain all survived and only experienced "mild" symptoms. The study did not include humanized mice.

The COVID researchers said they created the new strain to "help fight against future pandemics," the Boston Herald reported. However, several scientists slammed the new virus manipulation research as dangerous.

"This should be totally forbidden, it's playing with fire," Professor Shmuel Sharipa, a leading scientist in the Israeli government, was quoted as saying by The Daily Mail.

Dr. Richard Ebright, a chemist at Rutgers University in New Brunswick, New Jersey, classified the new COVID strain as a product of "gain of function research." He then called for better oversight of research concerning the "potential pandemic pathogen."

"If we are to avoid a next lab-generated pandemic, it is imperative that oversight of enhanced potential pandemic pathogen research be strengthened," Ebright told the outlet.

By definition, a gain of function research refers to the practice of manipulating a virus to be more infectious or deadly. Gain of function research is thought to be the origin of COVID-19.

Researchers at Boston University, however, said their research is not gain of function research and noted that their study "made the virus replicate less dangerous."

COVID-19 was first detected in a wet market in Wuhan. Many believe it was engineered by researchers at the Wuhan Institute of Virology, though the theory remains unproven. Other reports suggest COVID-19 spread naturally in a zoonotic jump from animals to humans.

The new research, which is published on BioRXiv, was approved by the Institutional Biosafety Committee, which consists of scientists and local community members, and the Boston Public Health Commission. The study has not yet been peer-reviewed.