TThe recent resurgence of polio has been hit by some of the bombardment of epidemic thunder. It was in 1979 that Polio has been officially declared eradicated In the United States – an early step in a multigenerational effort to eradicate disease worldwide. On July 21, however, the New York State Department of Health Announce a case of polio In an unvaccinated man in Rockland County, the circulating polio virus has since been found in sewage there and in neighboring Orange County, as well as in New York City. In London, the virus was also found in wastewater in February, and in Jerusalem, a case of the disease appeared in the same month.
The three cases, though seemingly isolated, point to a worrying trend – one that contrasts with more than three decades of progress in eradicating the disease. In 1988, polio was endemic to 125 countries and killed or paralyzed 350,000 people – mostly children – every year. According to the World Health Organization (Who is the). But thanks to a massive vaccination campaign by the World Health Organization, Rotary International, UNICEF, the US Centers for Disease Control and Prevention (CDC), and more, polio is now epidemic in only two countries – Afghanistan and Pakistan – that have experienced Only 18 cases between them So far this year.
However, polio is creeping up again, and health officials are now on alert for what Paul Andino Pavlovsky, professor of microbiology and immunology at the University of California, San Francisco, calls a “silent epidemic” of the disease worldwide. “This is just the tip of the iceberg,” he warns.
Yvonne Moldanado, professor of global health and infectious diseases at Stanford University School of Medicine, adds, “The case we saw [in New York] It was unusual but a red flag to be on the lookout for a possible outbreak. We are at risk of developing more cases of paralysis.”
The bad news is that polio is catching up with us again. The good news is that just last year, a new vaccine was added to the existing polio arsenal — a vaccine that, if deployed properly, could stop a new global spread of polio before it starts. Whatever the case, the emergence of the disease has raised a set of challenges – all of which must be met if we are to contain polio.
What is behind the current outbreak?
Multiple factors have played a role in the resurgence of polio – not least complacency, especially in the United States and other developed countries. When the majority of people alive do not experience a particular disease condition, it is easy to dismiss it. “People don’t remember polio, they don’t see it,” says Ian Lipkin, professor of epidemiology at Columbia University’s Mailman School of Public Health. “There is something about our species that just allows us to forget the importance of these things.”
This could lead to a slow erosion in compliance with vaccines – something that figures in the US corroborate nationwide, where 92.6% of children are fully vaccinated against polio by age 2, According to the Center for Disease Control and Prevention. Overall, this is an encouraging number, but vaccination rates vary from state to state and even from county to county. In Oklahoma, for example, polio vaccination rates are only 79.5%, and in South Carolina, it is 80.3%. In the Rockland County zip code where the polio case emerged in June, The vaccination rate stands at an alarmingly low level of 37.3%..
The COVID-19 pandemic has happened too Played a role in the recurrence of the disease. “During the COVID era, families didn’t see their doctors or pediatricians as often,” says Dr. William Schaffner, MD, professor of infectious diseases at Vanderbilt University School of Medicine in Nashville, Tennessee. This has resulted in children falling behind in routine immunization schedules.”
According to Moldanado, the decline has been minimal, with only a 1% drop in polio vaccination rates among children since the pandemic began. But when it comes to infectious diseases, even one percent can be very significant. “It translates to tens of thousands of children who are not fully vaccinated, and these children are at risk of developing diseases that really shouldn’t exist in well-resourced countries,” Moldañado says.
The vaccine paradox
The paradox of the return of polio is that the vaccination campaign itself is CDC . Estimates Preventing 16 million paralysis and 1.5 million deaths since 1988 is partly responsible for the new resurgence. There are two types of polio vaccines. The first, known as the inactivated polio vaccine (IPV) – which is given by injection – uses a dead virus to identify the body with disease and prime it to recognize and attack the live virus if it is ever exposed. The other, known as the oral polio vaccine (OPV) – which is given by mouth – uses an attenuated or weakened virus that can do the same job of preparing the immune system, without actually causing disease. The advantage of the oral vaccine is that it is easier and cheaper to administer, which is why it is used in global eradication campaigns. The major drawback is that in rare cases, a weakened vaccine can revert to its virulent strain. This can lead to illness in the person who has received the vaccine, and even if it does not, the reactivated virus is shed in the stool, enters wastewater and potentially infects other people. For this reason, the United States switched to IPV exclusively in 2000—although cases of viral rebounds have been extremely rare.
“The raw estimate was that one in three million doses of oral vaccine given would cause polio in the United States before 2000,” Schaffner says. “It’s rare, but it’s not inconsequential.”
Actually it is not. Genetic sequencing revealed that the virus that caused the recent cases in New York and Jerusalem and was found in wastewater in London was called circulating vaccine-derived polio virus (cVDPV). So far this year, cVDPV has led to 535 more cases of polio in 18 other countries, to me Global Polio Eradication Initiative.
But IPV has its problems, too — in addition to being relatively difficult to manage. Since the ORV is taken orally, it establishes what is known as gut immunity. Assuming that the person receiving the vaccine is not among the unlucky few for whom the virus reverts to its virulent form, then there is no viral replication in the intestinal tract, and therefore no virus is shed in the feces. IPV protects the recipient from contracting polio, but does not prevent intestinal reproduction and spread if that person catches cVDPV.
Andino-Pavlovsky believes that sampling of wastewater in any part of the world where IPV is used will likely give rise to some of the circulating vaccine-derived polioviruses contracted, replicated and dumped by IPV recipients, putting unvaccinated people at risk. “In Europe, in America, in Australia – everywhere people are using an inactivated vaccine – it’s likely,” he says.
Even with drawbacks in both vaccines, vaccination is clearly better than no vaccination, because all vaccine recipients are protected from asymptomatic polio. But oral vaccine and oral polio are already in a state of tension, with one producing a vaccine-derived virus and the other contributing to its spread. For this reason, the World Health Organization and other global health organizations are calling for an eventual switch to IPV exclusively — a move that would mean that there would never be a vaccine-derived virus caught and shed.
“We need to stop giving the live virus until it stops spreading,” Moldañado says.
However, this is not practical at the moment – not while there are still millions of children and children who need vaccines in the developing world, where the IPV vaccine is still very expensive, and the skilled vaccinators who can give the injections are far fewer than the field workers who need To a little special training to give the drops in the mouth. As an interim solution, the World Health Organization, the Bill & Melinda Gates Foundation and the UK’s National Institute for Biological Standards and Control have come together to develop a new oral vaccine that is more stable than previous versions, reducing the potential for the attenuated virus to be used. In drops back to its malignant state.
Andino-Pavlovsky, who was part of the team that designed the vaccine, explains that it works by targeting the spot on the viral genome responsible for returning to virulence. In existing OPVs, this part of the genome needs to go through only one mutation to go from being harmless to dangerous.
“Basically what we’ve done is modify this sequence, so a single point mutation can’t cause a rebound; the virus now has to go through four or five different changes before it acquires a more virulent phenotype. Basically, it’s a numbers game,” he says. As described by Andino Pavlovsky previously to magazine temper nature“It’s like putting a virus in an evolutionary cage.”
A vaccine containing this virus began to be used in a cage at the end of 2021 and so far, Andino Pavlovsky says, more than 180 million doses have been administered in 13 countries. “The new vaccine is as effective as the previous vaccine in creating immunity,” he says, “[and is] able to stop the silent epidemic.”
The goal, eventually, is to push polio off the cliff to extinction – as was smallpox in 1980 – with the slow phase-out of all oral polio vaccine, global use of polio, and the eradication of any form of polio virus circulating in anywhere in the world. The current return of the disease is a reminder that this task is almost unfinished. Until that happens, an ancient catastrophe will haunt us again.
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