For the primary time in 20 years, the CDC is discussing giving a polio vaccine by mouth to cease the outbreak in New York

The Centers for Disease Control and Prevention is considering using the oral polio vaccine for the first time in more than 20 years to halt an outbreak in the New York City area that paralyzed an adult over the summer.

“We are in discussions with our colleagues in New York State and New York City about using nOPV,” said Dr. Jannell Routh, the CDC’s indigenous polio team leader, referring to the novel oral polio vaccine.

“It will be a process. It’s not something we can pull the trigger on and make it appear overnight,” Routh told CNBC. “There will be a lot of thought and discussion about reintroducing an oral polio vaccine in the United States,” she said.

The New York State Department of Health said in a statement it is working with the CDC on possible future options for responding to the outbreak.

U.S. drug regulators pulled the oral vaccine off shelves in 2000 because it contains a live — but weakened — strain of the virus that, on rare occasions, can mutate into a virulent form that’s contagious and potentially affecting people who aren’t vaccinated are paralyzed.

Scientists believe this latest outbreak was caused by someone who was vaccinated abroad with the live virus and started a chain of transmission that eventually made its way to the United States. New York wastewater samples are linked to earlier samples in London and Jerusalem. Where the transmission originally began is unclear. While the oral vaccine doesn’t usually cause polio that cripples people, this one did because it was able to mutate into more virulent strains as it spread among people who weren’t vaccinated.

The US currently uses the inactivated polio vaccine, which is given by injection and contains chemically killed viruses that cannot replicate, mutate, or cause disease. While New York state health officials have launched a immunization campaign using the inactivated polio vaccine, this vaccine has not stopped this outbreak.

The CDC has established a working group within its Committee of Independent Vaccine Advisors to develop criteria for when the novel oral polio vaccine may need to be used to halt the current New York City-area outbreak and potential future ones. The working group met publicly for the first time on Wednesday and includes experts from New York.

“Because this outbreak occurred in New York, it was determined that we needed to re-treat polio. It really is that simple,” said Dr. Oliver Brooks, working group chair and chief medical officer at Watts Healthcare in Los Angeles.

The problem is that while the inactivated vaccine is highly effective at preventing paralysis, it does not stop transmission of the virus. The oral polio vaccine is much more effective at stopping transmission of the virus and is usually used to suppress outbreaks.

The poliovirus strain currently circulating in the New York City metropolitan area mutated from and is genetically linked to the Sabin type 2 strain used in an older version of the oral polio vaccine.

The US would use the novel oral polio vaccine, if needed, which is a safer and newer version that is more stable and carries a much lower risk of mutating into a strain of the virus that can spread and cause disease in people who are unvaccinated can cause Routh.

The novel oral polio vaccine was developed to stop poliovirus outbreaks caused by the less stable older version of the vaccine, according to the Global Polio Eradication Initiative. More than 450 million doses have been administered in 21 countries around the world.

Any decision to use the novel oral polio vaccine would require either approval or emergency use authorization from the Food and Drug Administration. CNBC has reached out to the FDA for comment.

An unvaccinated adult in Rockland County, New York, was paralyzed in June after contracting the poliovirus. It was the first known US case in almost a decade and the first in New York since 1990. So far there have been no other cases of paralysis, although New York state health officials have warned that unvaccinated people are at serious risk and should get up immediately updated on their recordings.

The New York State Department of Health has detected poliovirus in sewage in several counties in the New York City area since April and as recently as September. The virus was detected in 70 sewage samples in Rockland, Sullivan, Orange, Nassau, Kings and Queens counties.

The US was declared polio-free in 1979.

New York Gov. Kathy Hochul declared a state of emergency in September, and Health Commissioner Dr. Mary Bassett declared the spread of poliovirus an imminent public health threat.