Now, in an unexpected twist to the decades-long effort to eradicate the virus, authorities in Jerusalem, New York and London have discovered evidence that polio is spreading there. The original source of the virus? The oral vaccine itself.
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Scientists have long known about this extremely rare phenomenon. This is why some countries have switched to other polio vaccines. But these accidental infections from oral formula are becoming more glaring as the world moves closer to eradicating the disease and the number of polio cases caused by the wild or circulating virus plummets. Story continues below ad As of 2017, there have been 396 cases of polio caused by the wild virus, compared to more than 2,600 linked to the oral vaccine, according to data from the World Health Organization and its partners. “We’re basically replacing the wild virus with the virus in the vaccine, which is now leading to new cases,” said Scott Barrett, a Columbia University professor who has studied polio eradication. “I would have assumed that countries like the UK and the US would be able to stop transmission fairly quickly, but we also thought about monkeypox.” 2:20 Parallels with COVID-19: Polio debacle helped shape vaccine safety in 1950s Parallels with COVID-19: Polio debacle helped shape vaccine safety in 1950s – 23 October 2021 The latest cases represent the first time in several years that the vaccine-associated polio virus has appeared in rich countries. Earlier this year, officials in Israel found polio in an unvaccinated 3-year-old boy who suffered from paralysis. Several other children, almost all unvaccinated, were found to have the virus but no symptoms. Story continues below ad In June, British authorities reported finding evidence in sewage that the virus was spreading, although no human infections had been identified. Last week, the government said all children in London aged 1 to 9 will be offered a booster shot. In the US, an unvaccinated young adult suffered paralysis in his legs after contracting polio, New York City officials revealed last month. The virus has also appeared in the sewers of New York City, suggesting it is spreading. But officials said they are not planning a booster campaign because they believe the state’s high vaccination rate should provide enough protection. Genetic analyzes showed that the viruses in the three countries were all “vaccine-derived,” meaning they were mutated versions of a virus that came from the oral vaccine. The controversial oral vaccine has been used since 1988 because it is cheap, easy to administer _ two drops go directly into children’s mouths _ and is 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 for full immunization.) In extremely rare cases, the weakened virus can also sometimes mutate into a more dangerous form and cause outbreaks, especially in places with poor sanitation and low levels of vaccination. These outbreaks usually begin when people who are vaccinated pass live virus from the vaccine in their stool. From there, the virus can spread through the community and, over time, mutate into a form that can paralyze people and start new epidemics. Story continues below ad Many countries that eliminated polio switched to injectable vaccines containing 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. “We probably never could have overcome polio in the developing world without (oral polio vaccine), but that’s the price we’re paying now,” said Dr. Paul Offitt, director of the Vaccine Education Center at Children’s Hospital of Philadelphia. “The only way we’re going to eliminate polio is to eliminate the use of the oral vaccine.” Aidan O’Leary, director of the WHO’s polio division, described the discovery of the spread of polio in London and New York as “a big surprise”, saying officials have focused on eradicating the disease in Afghanistan and Pakistan, where they have killed health workers. to immunize children and where conflict has made access impossible in some areas. 5:25 Canada could test sewage for polio ‘if the need arises’: Tam Canada could test sewage for polio ‘if the need arises’: Tam – August 12, 2022 However, O’Leary said he was confident Israel, Britain and the US would quickly shut down the newly identified cases. Story continues below ad 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 approximately 350,000 cases of wild polio per year. So far this year, 19 cases of wild polio have been reported, all in Pakistan, Afghanistan and Mozambique. In 2020, the number of vaccine-linked polio cases peaked at more than 1,100 spread across dozens of countries. It has since dropped to around 200 this year so far. Last year, the WHO and its partners also began using a newer oral polio vaccine, which contains a live but weakened virus that scientists believe is less likely to mutate into a dangerous form. But supplies are limited. To stop polio in Britain, the US and Israel, what is needed is more vaccination, experts say. That’s something Columbia University’s Barrett worries could be a challenge in the age of COVID-19.
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“What’s different now is the decline in trust in the authorities and political polarization in countries like the US and the UK,” Barrett said. “The assumption that we can rapidly increase vaccination numbers may be more difficult now.” Oyewale Tomori, a virologist who helped direct Nigeria’s effort to eradicate polio, said that in the past, he and his colleagues avoided describing cases as “vaccine-induced,” wary that it would make people fearful. the vaccine. Story continues below ad “All we can do is explain how the vaccine works and hope people understand that immunization is the best protection, but it’s complicated,” Tomori said. “In hindsight, maybe it would have been better not to use this vaccine, but at the time, no one knew it would turn out like this.” © 2022 The Canadian Press
