BPrior to this year, polio was not an urgent threat. The disease was eliminated in the United States in 1979, and thanks to a global vaccination campaign, it was eradicated Endemic (though not widespread) in only two countries– Pakistan and Afghanistan.
But the calculus changed in 2022. In July, an unprotected man in New York State Contracted polio. And this year, the polio virus spread to wastewater in London, Jerusalem, and – most recently on October 28 – in New York City and several surrounding counties. Researchers wrote in Report New York results announced. Anyone who falls into this category must “complete the vaccination series as soon as possible”.
Ironically, one of the two types of polio vaccine plays a role in the recent spread. To combat the outbreak, the US government is considering introducing a third type of vaccine. Here’s what you need to know about two different polio vaccines, the new looming vaccine, and how to keep your family safe.
The differences between the two polio vaccines
The first polio vaccine, developed by Dr. Jonas Salk and approved in the United States in 1955, is known as the inactivated polio vaccine (IPV). It is given by injection and uses killed polioviruses to inform the immune system of the disease and prime it to recognize live wild virus if it is exposed to any virus.
The second, developed by Dr. Albert Sabin and approved in the United States in 1963, is known as the oral polio vaccine (OPV) and uses a weakened – or weakened – strain of the virus: a strain that cannot cause disease but can do the same job as preparing an oral polio vaccine. Immunosuppressants such as IPV.
OPV has two big advantages: it is easier and cheaper to administer – with just a few drops on the tongue – than IPV. This is why it was the vaccine of choice for Global Polio Eradication Initiative (GPEI) – A consortium of Rotary International, World Health Organization (WHO), UNICEF, CDC, and other health organizations that conduct massive international vaccination campaigns. But it comes with a drawback too. In rare cases, the live virus in the oral vaccine can revert to virulence, either causing polio in the person who received the drops, or shed in their faeces and spread into the environment. Small, fading traces of faeces on hands or surfaces – even after washing hands – can be enough to transmit the virus in the rare cases where such shedding does occur. So far in 2022, there have been 555 cases of polio in 21 countries caused by the so-called vaccine-derived polio virus (cVDPV). to me GPEI. For this reason, the United States gradually phased out the use of the oral vaccine in 2000. But most of the world still uses it.
“In countries where they continue to use the oral vaccine, you have more cases of vaccine-related polio than you do with the wild virus,” says Dr. William Schaffner, professor of infectious diseases at Vanderbilt University School of Medicine.
None of this means that the oral vaccine is more dangerous than a boon. Return to virulence is rare—occurring in about one in three million doses given, according to Schaffner—and not every case of reflux leads to polio. Since the Global HIV Initiative began its work in 1988, it is estimated that the oral vaccine has prevented 16 million paralysis and 1.5 million deaths. However, the virus that infected a Rockland County man and appeared in New York sewage is just that type of vaccine-derived virus, presumably brought into the country by someone from a part of the world using oral polio vaccine. The London and Jerusalem strains are also genetically related to the New York strain, indicating the origin of the oral polio vaccine.
But IPV also has a drawback, in addition to the difficulty of comparison and the expense of management. Oral vaccine, since it is taken orally, confers what is known as intestinal immunity – this means that assuming that the person receiving the vaccine is not among the unfortunate few in whom the virus turns virulent, there is no viral replication in the intestinal tract and therefore faeces is forbidden , even if that person picked up cVDPV from someone else. The cerebral palsy vaccine does not establish gut immunity; The vaccine may forever prevent the person receiving the vaccine from contracting polio, but it does not prevent intestinal replication if that person catches cVDPV. This presents a risk, because a person vaccinated with IPV can further spread cVDPV.
What has long been needed is a new oral vaccine: a vaccine that establishes gut immunity but is less likely to return to virulence. And such a vaccine now exists.
New Oral Polio Vaccine
In 2021, researchers working with the Bill & Melinda Gates Foundation; National Institute for Biological Standards and Control (NIBSC) in the UK; University of California, San Francisco; and US Food and Drug Administration (FDA) New Oral Polio Vaccine Developed Known as nOPV2. (The number “2” in the name indicates that it specifically targets the type 2 polio strain — the only remaining of the three strains that existed before. Types 1 and 3. have been eliminated) The nOPV2 vaccine — which has not Occurs after approved for use in the United States – includes an attenuated virus that has been genetically engineered to be more stable than the virus used in the current OPV oral vaccine. Rather than having to undergo only one mutation to return to virulence, the virus must mutate in nOPV2 at five different points on its genome before it represents a threat.
“It’s a virus that can still accumulate mutations like any virus,” says Raul Andino Pavlovsky, a professor of microbiology and immunology at the University of California, San Francisco, who was involved in developing the vaccine. “But it’s a bit inactivated, so it doesn’t develop as quickly as the original oral polio vaccine, and so it’s much safer.”
Actually safer. “We’ve incorporated changes to make it more faithful as we copy it,” says Andrew McAdam, principal scientist at NIBSC, who also worked on the new vaccine. “With our virus, we’ve never seen a rebound to virulence in lab tests, in animals or in humans.” In March 2021, the new vaccine went into operation in Africa, and since then, 500 million doses have been administered, mainly in Africa, Afghanistan and Pakistan. At the time, says McAdam, “there was not a single confirmed case of vaccine-related polio [with the nOPV2]. “
How to protect yourself from polio
For now, IPV remains the best way to protect yourself and your family. Currently, 92.5% of American children have received the three prescribed doses of injections by the age of two, According to the Center for Disease Control and Prevention. But vaccination rates It varies greatly across the country. In Idaho, the number is 86.6%, for example, and in the District of Columbia, only 80.4%. In the zip code that a Rockland County man who recently contracted polio lives in, the vaccination rate remains steady At a dangerously low level 37.3%. For this reason, the Centers for Disease Control and Prevention is considering allowing the new vaccine to be used in the United States, hoping to halt the current spread of vaccine-derived poliovirus by establishing gut immunity in people receiving nOPV2 drops. The new vaccine may be better than the IPV vaccine because of that extra layer of immunity it provides, but more than 20 years of vaccine policy has not been quickly repealed — especially since the IPV vaccine has been so successful in the United States — and the US government is making the time to decide whether take this step or not.
“Out of great caution, the CDC is looking at all options to stop the spread of the polio virus in New York,” Janelle Roth, CDC team leader and local polio surveillance, said in a statement to TIME. On October 19, Roth said, the CDC and New York State formed a polio working group and “begin preliminary discussions to consider criteria under which nOPV2 can be used in areas where poliovirus is persistently circulating.” Roth added that any use of nOPV2 would require emergency use authorization from the Food and Drug Administration.
Neither Roth nor other CDC spokespeople will speculate when the polio working group will reach a conclusion on whether to recommend nOPV2. “Currently, immunizing those at risk in affected and surrounding communities with IPV, which is a very safe and effective vaccine, remains a priority,” Roth said. “Three doses of IPV provide 99% protection against paralysis caused by poliovirus infection.” .
nOPV2 is new, and the outbreak in New York is still newer. But for now, at least, it’s an old precaution that’s the front line in protecting the weak.
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