![]() ![]() When the virus is transmitted to a susceptible host, it can replicate. But in some very rare instances-1 in maybe 2.5 million cases-when you administer the polio vaccine, you could have a scenario where the OPV virus is transmitted from somebody who received the vaccine to somebody who is susceptible, meaning they have no immunity to polio. In a number of countries outside the U.S., OPV is the mainstay of vaccination programs for a lot of reasons: It’s easy to administer for community campaigns. The second type is the inactivated polio vaccine (IPV), which contains a killed version of the virus. Even though it’s attenuated or weakened, it’s still the live virus. One of the commonly used vaccines is what we call the oral polio vaccine (OPV). To answer that question, we have to talk about the two types of vaccines that we have for polio. How does that happen? How does a vaccine virus turn into an infection? We do see cases of vaccine-derived poliovirus-which is different from the wild poliovirus and which is what we see emerging in more countries. We also have seen about a 99%reduction in cases, to fewer than 15,000, than what was recorded at the onset of the eradication program.īut the eradication effort has also created some challenges, particularly for the viruses derived from the polio vaccine itself. Right now, the wild poliovirus is endemic in two countries: Pakistan and Afghanistan. Since that time, there have been concerted efforts through vaccination programs and community engagement to address polio. At that point, there were fewer than 50,000 cases reported annually. In 1988, the world got together to eradicate polio. What’s the history of polio around the world? That’s how we think about this in the United States-the pictures of kids in the iron lungs from paralytic polio. ![]() In very rare cases-maybe 1 in 100 to 1 in 500 cases-there is what you call acute flaccid paralysis, which usually involves weakness and paralysis of the muscles of the lower limbs. But about 25% of people that get infected could have meningitis, with neck stiffness and a lot of pain. ![]() In most cases, it causes a mild form of illness that presents almost like the regular flu or some other kind of minor viral infection-basically fever, muscle ache, and headache. In its severest form, polio causes damage to the nerves that control some of our voluntary muscles, including the muscles we use to walk, hold things, breathe, talk, and so on. The virus is transmitted by ingesting contaminated food or drinking contaminated water, through what we call the oral-fecal route. In this Q&A, adapted from the episode of Public Health On Call, Alonge talks with Joshua Sharfstein about the current polio outbreaks and what we can do about them. Olakunle Alonge, MD, PhD ’13, MPH ’09, an associate professor in International Health, studies global polio eradication efforts. saw its first case of paralytic polio in decades. But now, evidence of polio outbreaks is showing up in wastewater in U.S. Thanks to massive vaccination campaigns around the world, polio cases dropped by 99% since the late 1980s and, until recently, remained endemic in only two countries. In 1961, an oral polio vaccine (OPV) containing a weakened or “attenuated” live version of the virus made widespread vaccination much easier around the globe because it could be administered by oral drops and not through needles. In 1955, an inactivated polio vaccine (IPV), which contained a “killed” version of the virus and was delivered as a shot, was introduced. Just a generation or so ago, tens of thousands of people in the U.S.-mainly children-were afflicted by paralytic poliovirus. ![]()
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