LONDON (AP) — For years, global fitness officials have used billions of drops of an oral vaccine in a remarkably effective crusade to eliminate polio in the last remaining strongholds: deficient and politically volatile corners of the world.
Now, in an unexpected twist in the decades-long effort to eliminate the virus, the government of Jerusalem, New York and London has exposed evidence that polio is spreading there.
The original of the virus? The oral vaccine itself.
Scientists have long known about this incredibly rare phenomenon. This is why some countries have switched to other polio vaccines. But those accidental oral formula infections are becoming more and more egregious as the world approaches the elimination of the disease and the number of polio cases. caused by droplets of wild or naturally circulating viruses.
Since 2017, there have been 396 cases of polio caused by the wild virus, to more than 2600 related to the oral vaccine, according to figures from the World Health Organization and its partners.
“We’re necessarily replacing the wild virus with the vaccine virus, which is now leading to new outbreaks,” said Scott Barrett, a Professor at Columbia University who has studied polio eradication. to be to prevent transmission pretty quickly, but we also have an idea of that about monkeypox. “
The latest incidents mark the first time in several years that the vaccine-linked polio virus has emerged in countries.
Earlier this year, Israeli authorities detected polio in an unvaccinated 3-year-old boy suffering from paralysis. Several other children, almost all unvaccinated, have been shown to bring the virus, but without any symptoms.
In June, the UK government reported finding evidence in sewage that the virus was spreading, with no infections identified in other people. Last week, the government said all children in London aged 1 to 9 would receive a booster shot.
In the United States, an unvaccinated young adult suffered leg paralysis after his polio became inflamed, New York City officials revealed last month. The virus also appeared in New York City sewers, suggesting it is spreading. they were not making plans for a booster crusade because they believed the state’s highest vaccination rate offered enough protection.
Genetic analyses showed that viruses in all 3 countries were “vaccine-derived”, they were mutated versions of an oral vaccine virus.
The oral vaccine in question has been used since 1988 because it is cheap, easy to administer – two drops are put directly into the mouths of children – and more so in entire protective populations where polio spreads. It is a weakened form of the live virus.
But it can also cause polio in about two to four young people consistent with 2 million doses. (Four doses are required to be fully immunized. ) In incredibly rare cases, the weakened virus can also mutate into a more harmful form and cause outbreaks, especially in places where sanitation is poor and vaccination levels are low.
These outbreaks begin when other vaccinated people release the live vaccine virus into their stool. From there, the virus can spread within the network and, over time, take on a form that can paralyze other people and cause new epidemics.
Many countries that have eliminated polio have switched to injectable vaccines containing a virus that died decades ago to avoid such risks; the Nordic countries and the Netherlands have never used the oral vaccine. The ultimate goal is to move the world to vaccines once wild polio is eradicated, however, some scientists say the substitution will take place sooner.
“We probably would never have been able to fight polio in the world ahead without the (oral polio vaccine), but that’s the value we’re paying now,” said Dr. Paul Offit, director of the Vaccine Education Center at Children’s Hospital of Philadelphia. “The only way to eliminate polio is to eliminate the use of the oral vaccine. “
Aidan O’Leary, director of the WHO’s polio department, described the discovery of the spread of polio in London and New York as “a major surprise,” and said officials have focused on eliminating the disease in Afghanistan and Pakistan, where fitness staff have been killed. For the vaccination of young people and where the shock has made certain spaces impossible.
Still, O’Leary said he was sure of himself that Israel, Britain and the United States would temporarily end their newly known outbreaks.
The oral vaccine is credited with drastically 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 throughout the year. So far this year, there have been 19 cases of wild polio. , all in Pakistan, Afghanistan and Mozambique.
In 2020, the number of vaccine-related polio cases peaked at more than 1100 in dozens of countries. Since then, it has declined to around two hundred this year so far.
Last year, WHO and its partners also started a new oral polio vaccine, comprising a live but weakened virus that scientists say is less likely to mutate into a harmful form. But materials are limited.
To prevent polio in Britain, the United States and Israel, more vaccination is needed, experts say. This is something that The considerations of Barrett of Columbia University can be misleading in the covid-19 era.
“What is another now is a relief in accepting as true in government and political polarization in countries like the U. S. “The U. S. and the U. K. ,” Barrett said. The assumption that we can rapidly increase the number of vaccines could be more complicated now. “
Oyewale Tomori, a virologist who helped lead Nigeria’s polio efforts, said that in the past, he and his colleagues were reluctant to describe outbreaks as “vaccine-derived,” for fear that the vaccine would scare other people.
“All we can do is how the vaccine works and expect other people to perceive that vaccination is the most productive protection, but it’s complicated,” Tomori said. “In retrospect, maybe it would have been better not to use this vaccine, but at the time, no one knew it would happen like this. “
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