London - Global health officials and governments have fought for years to eradicate ‘Poliomyelitis’ or most commonly known as ‘Polio’. The surprise re-emergence of polio in many polio-free countries set an alarm in Jerusalem, New York and London.

The baffled officials now confirm the original source of the virus…the oral vaccine itself.

Scientists in countries with knowledge about this extremely rare phenomenon had switched to other polio vaccines.

Since 2017, there have been 396 cases of polio caused by the wild virus, versus more than 2,600 linked to the oral vaccine, according to figures from the World Health Organization and its partners.

“We are basically replacing the wild virus with the virus in the vaccine, which is now leading to new outbreaks,” said Scott Barrett, a Columbia University professor who has studied polio eradication.

Vaccine-connected polio in rich countries a first in years
Earlier this year, officials in Israel detected polio in an unvaccinated 3-year-old, who suffered paralysis.

In June, British authorities reported finding evidence in sewage that the virus was spreading, though no infections in people were identified. Last week, the government said all children in London ages 1 to 9 would be offered a booster shot.

In the U.S., an unvaccinated young adult suffered paralysis in his legs after being infected with polio, New York officials revealed last month. The virus has also shown up in New York sewers, suggesting it is spreading. But officials said they are not planning a booster campaign because they believe the state’s high vaccination rate should offer enough protection.

Genetic analyses showed that the viruses in the three countries were all “vaccine-derived,” meaning that they were mutated versions of a virus that originated in the oral vaccine.

The oral vaccine at issue has been used since 1988 because it is cheap, easy to administer — two drops are put directly into children’s mouths — and better at protecting entire populations where polio is spreading. It contains a weakened form of the live virus.

But it can also cause polio in about two to four children per 2 million doses. (Four doses are required to be fully immunized.) In extremely rare cases, the weakened virus can also sometimes mutate into a more dangerous form and spark outbreaks, especially in places with poor sanitation and low vaccination levels.

These outbreaks typically begin when people who are vaccinated shed live virus from the vaccine in their feces. From there, the virus can spread within the community and, over time, turn into a form that can paralyze people and start new epidemics.

Many countries that eliminated polio switched to injectable vaccines containing a killed virus decades ago to avoid such risks; the Nordic countries and the Netherlands never used the oral vaccine. The ultimate goal is to move the entire world to the shots once wild polio is eradicated, but some scientists argue that the switch should happen sooner.

The oral vaccine is credited with dramatically reducing the number of children paralyzed by polio. When the global eradication effort began in 1988, there were about 350,000 cases of wild polio a year.

In 2020, the number of polio cases linked to the vaccine hit a peak of more than 1,100 spread out across dozens of countries. It has since declined to around 200 this year so far.

To stop polio in Britain, the U.S. and Israel, what is needed is more vaccination, experts say. That is something Columbia University’s Barrett worries could be challenging in the COVID-19 era.
-AP