Prince.Skeletor
Don’t Be Like He-Man
Cases of paralysis in the U.S. and Israel suggest vaccine-derived poliovirus has infected many people
The discovery of poliovirus in New York state, London and Jerusalem this year has taken many by surprise — but public-health researchers fighting to eradicate the disease say it was only a matter of time.
“No country in the world is immune to the effects of polio,” says Zulfiqar Bhutta, a global-health researcher at the Aga Khan University in Karachi, Pakistan. “It’s all interconnected.”
The virus found in these regions is derived from an oral polio vaccine used in some countries. So far, only two cases of polio-related paralysis have been reported, in Jerusalem in February and New York in June; the New York infection was the first such US case in nearly a decade. But wastewater samples in all three areas suggest that the virus is circulating more widely.
Polio causes irreversible paralysis in less than one in 200 of the susceptible people it infects, so the cases of paralysis suggest that many other people there have been infected, says Walter Orenstein, who studies infectious diseases at Emory University in Atlanta, Georgia. “Cases like that are just the tip of the iceberg,” he says. “It’s very concerning.”
Wild poliovirus circulates in only two countries — Afghanistan and Pakistan — where this year nine cases had been reported by June.
But vaccine-derived poliovirus appears periodically elsewhere, particularly in Africa and Asia. These cases come from a widely used oral vaccine that contains live, weakened virus that sometimes mutates to a dangerous form capable of infecting the nervous system.
Neither the United States nor the United Kingdom use that vaccine, opting instead for an injectable vaccine containing inactivated virus. This vaccine can keep the virus from infecting the nervous system, but it is not as effective as the oral virus at reducing viral shedding and halting transmission, says Raul Andino-Pavlovsky, a microbiologist at the University of California, San Francisco.
High polio vaccination rates in the United Kingdom, Israel and the United States mean that most children will be spared the virus’s worst effects (about 94% of US 5- and 6-year-olds are vaccinated). But unvaccinated people are vulnerable to the illness.
“This virus is very, very good at finding unvaccinated individuals,” says Orenstein. In the 1990s, a poliovirus outbreak in the Netherlands established a foothold in a community with a relatively low vaccination rate, despite the country’s overall vaccination coverage of more than 90%, says Oliver Rosenbauer, a spokesperson for the Global Polio Eradication Initiative of the World Health Organization (WHO) in Geneva, Switzerland. The outbreak resulted in 2 deaths and 59 cases of paralysis, and occurred 14 years after the country’s last endemic case of polio.
The United States, Israel and the United Kingdom are all boosting vaccination efforts, which should fill gaps created during the COVID-19 pandemic. This includes an ambitious effort to vaccinate all one-to-nine-year-olds in London.
This strategy should nip the outbreaks in the bud, says Grassly. But the campaigns in London and New York will use injectable vaccine, so they will not stop virus transmission.
This vaccine contains weakened poliovirus. But researchers used knowledge of the virus’s genome — including how an error-prone enzyme involved in replicating the genome can generate genetic changes — to create a suite of mutations that keep the virus from regaining its ability to infect the nervous system. “It’s like putting the virus in an evolutionary cage,” says Andino-Pavlovsky, who helped to design the vaccine.
That vaccine has not yet undergone large-scale human testing, and has not been approved by UK or US regulators. But more than 100 million people have received it, says Andino-Pavlovsky, with no signs of vaccine-derived poliovirus emerging.
www.scientificamerican.com
The discovery of poliovirus in New York state, London and Jerusalem this year has taken many by surprise — but public-health researchers fighting to eradicate the disease say it was only a matter of time.
“No country in the world is immune to the effects of polio,” says Zulfiqar Bhutta, a global-health researcher at the Aga Khan University in Karachi, Pakistan. “It’s all interconnected.”
The virus found in these regions is derived from an oral polio vaccine used in some countries. So far, only two cases of polio-related paralysis have been reported, in Jerusalem in February and New York in June; the New York infection was the first such US case in nearly a decade. But wastewater samples in all three areas suggest that the virus is circulating more widely.
Polio causes irreversible paralysis in less than one in 200 of the susceptible people it infects, so the cases of paralysis suggest that many other people there have been infected, says Walter Orenstein, who studies infectious diseases at Emory University in Atlanta, Georgia. “Cases like that are just the tip of the iceberg,” he says. “It’s very concerning.”
Wild poliovirus circulates in only two countries — Afghanistan and Pakistan — where this year nine cases had been reported by June.
But vaccine-derived poliovirus appears periodically elsewhere, particularly in Africa and Asia. These cases come from a widely used oral vaccine that contains live, weakened virus that sometimes mutates to a dangerous form capable of infecting the nervous system.
Neither the United States nor the United Kingdom use that vaccine, opting instead for an injectable vaccine containing inactivated virus. This vaccine can keep the virus from infecting the nervous system, but it is not as effective as the oral virus at reducing viral shedding and halting transmission, says Raul Andino-Pavlovsky, a microbiologist at the University of California, San Francisco.
High polio vaccination rates in the United Kingdom, Israel and the United States mean that most children will be spared the virus’s worst effects (about 94% of US 5- and 6-year-olds are vaccinated). But unvaccinated people are vulnerable to the illness.
“This virus is very, very good at finding unvaccinated individuals,” says Orenstein. In the 1990s, a poliovirus outbreak in the Netherlands established a foothold in a community with a relatively low vaccination rate, despite the country’s overall vaccination coverage of more than 90%, says Oliver Rosenbauer, a spokesperson for the Global Polio Eradication Initiative of the World Health Organization (WHO) in Geneva, Switzerland. The outbreak resulted in 2 deaths and 59 cases of paralysis, and occurred 14 years after the country’s last endemic case of polio.
The United States, Israel and the United Kingdom are all boosting vaccination efforts, which should fill gaps created during the COVID-19 pandemic. This includes an ambitious effort to vaccinate all one-to-nine-year-olds in London.
This strategy should nip the outbreaks in the bud, says Grassly. But the campaigns in London and New York will use injectable vaccine, so they will not stop virus transmission.
This vaccine contains weakened poliovirus. But researchers used knowledge of the virus’s genome — including how an error-prone enzyme involved in replicating the genome can generate genetic changes — to create a suite of mutations that keep the virus from regaining its ability to infect the nervous system. “It’s like putting the virus in an evolutionary cage,” says Andino-Pavlovsky, who helped to design the vaccine.
That vaccine has not yet undergone large-scale human testing, and has not been approved by UK or US regulators. But more than 100 million people have received it, says Andino-Pavlovsky, with no signs of vaccine-derived poliovirus emerging.
New Polio Outbreaks Worldwide Put Scientists on Alert
Cases of paralysis in the U.S. and Israel suggest vaccine-derived poliovirus has infected many people
www.scientificamerican.com