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posted by janrinok on Wednesday January 01 2020, @03:17PM   Printer-friendly
from the back-to-the-drawing-board dept.

Polio eradication program faces hard choices as endgame strategy fails:

The "endgame" in the decades-long campaign to eradicate polio suffered major setbacks in 2019. While the effort lost ground in Afghanistan and Pakistan, which recorded 116 cases of wild polio—four times the number in 2018—an especially alarming situation developed in Africa. In 12 countries, 196 children were paralyzed not by the wild virus, but by a strain derived from a live vaccine that has regained its virulence and ability to spread. Fighting these flare-ups will mean difficult decisions in the coming year.

The culprit in Africa is vaccine-derived polio virus type 2, and the fear is that it will jump continents and reseed outbreaks across the globe. A brand new vaccine is now being rushed through development to quash type 2 outbreaks. Mass production has already begun, even though the vaccine is still in clinical trials; it could be rolled out for emergency use as early as mid-2020. At the same time, the Global Polio Eradication Initiative (GPEI) is debating whether to combat the resurgent virus by re-enlisting a triple-whammy vaccine pulled from global use in 2016. That would be a controversial move, setting back the initiative several years, as well as a potential public relations disaster—an admission that the carefully crafted endgame strategy has failed.

"All options are on the table," says viro-logist Mark Pallansch of the U.S. Centers for Disease Control and Prevention, one of the five partner organizations in GPEI. "We are clearly in the most serious situation we have been in with the program," adds Roland Sutter, who recently stepped down as the director of polio research at the World Health Organization (WHO).

The heart of the problem is the live oral polio vaccine (OPV), the workhorse of the eradication program—the only polio vaccine powerful enough to stop viral circulation. Given as two drops into a child's mouth, OPV for decades contained a mix of three weakened polio viruses, one for each of the three wild serotypes that have long plagued humanity. All three serotypes in the vaccine have the potential to revert to more dangerous versions; that's why the endgame strategy calls for deploying OPV in massive campaigns to eradicate the wild virus, then ending its use entirely.

Wild serotype 2 was last sighted in 1999, so in 2016, as a first step in the endgame, all 155 countries using OPV replaced the trivalent version with a bivalent one, lacking the type 2 component. Announced with great fanfare, "the switch" was billed as the biggest vaccine rollout ever. Some type 2 outbreaks would inevitably occur for several years, GPEI realized, but those would be fought, somewhat paradoxically, by rushing in essentially the same vaccine that gave rise to them in the first place: a live, monovalent vaccine targeted against type 2 (mOPV2). If used in well-run campaigns, and only in outbreak regions, mOPV2 could stop outbreaks without seeding new ones, models suggested.

It often has not turned out that way. Instead of fading away, the number of type 2 outbreaks in Africa almost tripled from 2018 to 2019. Most of today's outbreaks stem from mOPV2 responses to previous ones, and GPEI is burning through its emergency stockpile of mOPV2 faster than it can be replenished. (Based on a small study in Mozambique, a WHO advisory panel recently recommended halving the dose to one drop if supplies run critically low, despite what it calls "a relatively weak level of evidence" that the smaller dose is as effective.) Meanwhile, the risk of explosive outbreaks around the globe is ratcheting up, because millions of children born since the switch have little or no immunity to type 2 virus.


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  • (Score: -1, Offtopic) by Anonymous Coward on Wednesday January 01 2020, @04:28PM

    by Anonymous Coward on Wednesday January 01 2020, @04:28PM (#938259)

    i blame it on overzealous scrubbing of "disturbing" video media from the internet ...
    if people could actually SEE what a suicide bombing does when they go off, or what mayhem drunk driving can cause or in this case what a polio infection looks like then maybe would "wake up"?
    what we get to see on the news is mostly half cleaned up already, leaves alot to be imagined and leaves a tasty of "not so bad afterall" (which is obviously wrong).
    so is more harm done (*shrug*-flake) or is "viewers discretion" banner better?

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