Global health officials have, for years, used billions of drops of an oral vaccine in a remarkably effective campaign that sought to wipe out polio in its last remaining strongholds, which are typically poor, politically unstable corners of the world.

However, in a surprising twist in the decades-long effort to eradicate the virus, authorities from Jerusalem, New York, and London, discovered evidence of polio outbreaks in their regions. The original source of the new infections was found to be the oral vaccine itself.

Polio Outbreak

Scientists have already known about this extremely rare phenomenon, which is why some countries have switched to other polio vaccines. However, these incidental infections from the formula are becoming more glaring as the world inches closer to the eradication of the disease.

Since 2017, authorities have already reported 396 cases of polio caused by the wild virus, compared to the over 2,600 linked to the oral vaccine, based on figures from the World Health Organization (WHO) and its partners.

In a statement, a Columbia University professor, Scott Barrett, who has studied polio eradication, said, "We are basically replacing the wild virus with the virus in the vaccine, which is now leading to new outbreaks. I would assume that countries like the UK and the U.S. will be able to stop transmission quite quickly, but we also thought about monkeypox," as per CTV News.

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The latest cases represent the first time in several years that a vaccine-connected polio virus has turned up in rich countries. Officials in Israel detected polio earlier this year in an unvaccinated three-year-old child who suffered paralysis.

Rare Risk of Oral Vaccine

Several other children, nearly all of whom were unvaccinated, were discovered to have been infected with the virus but had no symptoms. British authorities in June reported finding evidence in sewage that the virus was spreading in the region, though no infections in people were identified at the time.

According to the Associated Press, officials in the U.S. said that an unvaccinated young adult suffered paralysis in his legs after contracting polio. Furthermore, the virus has also been observed in New York sewers, suggesting that it was quickly spreading to other areas.

However, New York officials said that they are not yet planning a booster campaign because they believe the state's high vaccination rate should offer enough protection. On the other hand, genetic analyses showed that the viruses in the three countries were all "vaccine-derived," which meant that they were mutated versions of a virus that originated in the oral vaccine.

The oral formula being discussed has been used since 1988 because it is relatively cheap and easy to administer. It only has two drops that are put directly into children's mouths, and it is better at protecting entire populations where the virus is spreading. It is known to contain a weakened form of the virus.

The oral vaccine has been known to cause polio infection in about two to four children per 2 million doses. In extremely rare cases, the weakened version of the virus can sometimes mutate into a more dangerous form and spark outbreaks, especially in areas with poor sanitation and low vaccination levels, the Press Democrat reported.

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