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A Vaccinated Man Has Been Emitting Virulent Polio for 28 Years

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Fri, 2015-09-04 23:37 — Maeryn Obley

Children after an India polio-vaccination event, 2012. Courtesy CDC.gov

Image: Children after an India polio-vaccination event, 2012. Courtesy CDC.gov

phenomena.nationalgeographic.com - September 2nd, 2015 - Maryn McKenna

At the end of the decades-long global battle to eradicate polio from the planet, there is what looks like a simple goal: Render every person immune, by vaccination, for long enough that the disease can find no host in which to breed, and thus dies out. That was the strategy behind the eradication of smallpox, and since polio like smallpox affects only humans, it is supposed to work for that disease too.

Of course, it’s a little more complicated, and a paper published last week reveals one of the most challenging complications.

(VIEW COMPLETE ARTICLE)

Country / Region Tags: 
Global
General Topic Tags: 
Complexity
Disease
Health
Problem, Solution, SitRep, or ?: 
Problem
Groups this Group Post belongs to: 
Global Health

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Sat, 2015-09-05 09:18 — Kathy Gilbeaux

journals.plos.org - Published: August 27, 2015

CLICK HERE - Twenty-Eight Years of Poliovirus Replication in an Immunodeficient Individual: Impact on the Global Polio Eradication Initiative

. . . a paper published last week reveals one of the most challenging complications. It describes a British man of about 30 who, as a toddler, was given the full course of polio vaccines in use at the time—and who, for 28 years, has been harboring mutated, virulent poliovirus in his guts and shedding them in his feces. The researchers who wrote about him call him, and other patients like him, “an obvious risk to the eradication program.”

Abstract

There are currently huge efforts by the World Health Organization and partners to complete global polio eradication. With the significant decline in poliomyelitis cases due to wild poliovirus in recent years, rare cases related to the use of live-attenuated oral polio vaccine assume greater importance. Poliovirus strains in the oral vaccine are known to quickly revert to neurovirulent phenotype following replication in humans after immunisation. These strains can transmit from person to person leading to poliomyelitis outbreaks and can replicate for long periods of time in immunodeficient individuals leading to paralysis or chronic infection, with currently no effective treatment to stop excretion from these patients. Here, we describe an individual who has been excreting type 2 vaccine-derived poliovirus for twenty eight years as estimated by the molecular clock established with VP1 capsid gene nucleotide sequences of serial isolates. This represents by far the longest period of excretion described from such a patient who is the only identified individual known to be excreting highly evolved vaccine-derived poliovirus at present. Using a range of in vivo and in vitro assays we show that the viruses are very virulent, antigenically drifted and excreted at high titre suggesting that such chronic excreters pose an obvious risk to the eradication programme. Our results in virus neutralization assays with human sera and immunisation-challenge experiments using transgenic mice expressing the human poliovirus receptor indicate that while maintaining high immunisation coverage will likely confer protection against paralytic disease caused by these viruses, significant changes in immunisation strategies might be required to effectively stop their occurrence and potential widespread transmission. Eventually, new stable live-attenuated polio vaccines with no risk of reversion might be required to respond to any poliovirus isolation in the post-eradication era.

Glynis Dunn, Dimitra Klapsa, Thomas Wilton, Lindsay Stone, Philip D. Minor, Javier Martin 

DOI: 10.1371/journal.ppat.1005114

http://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1005114

 

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