60

According to this National Public Radio article:

For the first time, the number of children paralyzed by mutant strains of the polio vaccine are greater than the number of children paralyzed by polio itself.

So far in 2017, there have been only six cases of "wild" polio reported anywhere in the world. By "wild," public health officials mean the disease caused by polio virus found naturally in the environment. By contrast, there have been 21 cases of vaccine-derived polio this year.

Are the claims in this article accurate?

Community
  • 1
Roger
  • 3,031
  • 13
  • 28
  • 8
    I would keep in mind that this is being offered not as a "This is horrible - vaccine is worse than what it's trying to cure!" It's being offered as "the vaccine has been THIS successful at eradicating the disease, at large." – PoloHoleSet Mar 12 '19 at 23:06

1 Answers1

102

Numbers not exact, ratio plausible. This is a success story.

The WHO provides a queryable database on AFP / polio. I am a bit unclear on the exact meaning of the headers, so I'll list the 2017 global totals for all columns:

  • AFP (acute flaccid paralysis) cases: 104090
  • Non polio AFP Rate: 5.46
  • % Adequate stool collection: 89
  • Pending: 118
  • Wild poliovirus cases: 22
  • cVDPV cases: 96
  • Compatibles: 259

cVDPV stands for circulating vaccine-derived poliovirus.

So 96 cVDPV cases to 22 wild cases with 118 "pending" at least makes the claim's 21 to 6 cases plausible (assuming "at the point of writing").

This graph visualizes the progress of polio eradication:

enter image description here

(Tobus, Own work, CC BY-SA 4.0)

Note that cVDPV does not mean that the vaccinated person becomes ill. It means that viruses shedded by a freshly vaccinated person start infecting other, unvaccinated people. A fully vaccinated population would be immune from both types of polio.

Quoted from the WHO page, emphasis mine:

It takes a long time for a cVDPV to occur. Generally, the strain will have been allowed to circulate in an un- or under-immunized population for a period of at least 12 months. Circulating VDPVs occur when routine or supplementary immunization activities (SIAs) are poorly conducted and a population is left susceptible to poliovirus, whether from vaccine-derived or wild poliovirus. Hence, the problem is not with the vaccine itself, but low vaccination coverage. If a population is fully immunized, they will be protected against both vaccine-derived and wild polioviruses.

Since 2000, more than 10 billion doses of OPV have been administered to nearly 3 billion children worldwide. As a result, more than 13 million cases of polio have been prevented, and the disease has been reduced by more than 99%. During that time, 24 cVDPV outbreaks occurred in 21 countries, resulting in fewer than 760 VDPV cases.

Actually they felt they could remove the most problematic strain of the virus from the vaccination:

Until 2015, over 90% of cVDPV cases were due to the type 2 component in OPV. With the transmission of wild poliovirus type 2 already successfully interrupted since 1999, in April 2016 a switch was implemented from trivalent OPV to bivalent OPV in routine immunization programmes. The removal of the type 2 component of OPV is associated with significant public health benefits, including a reduction of the risk of cases of cVDPV2.

So allowing for the latency mentioned for cVDPV to actually occur, vaccine-derived polio cases can be expected to go down as well.

Community
  • 1
DevSolar
  • 19,034
  • 8
  • 77
  • 74
  • 11
    There's maybe a mismatch here where the quote in the question says 'paralysed by polio' but the data is more 'caught polio', which presumably doesn't have a 100% rate of paralysing people. I would perhaps hope that the live vaccine is with a strain that is unlikely to cause paralysis, so that rate would be lower even if it caused more infections, but I don't know anywhere enough about polio to know if that's possible. – mbrig Nov 16 '18 at 23:21
  • 16
    @mbrig [\[Paralysis\] occurs in less than 1% of all infections](https://ecdc.europa.eu/en/poliomyelitis/facts), so nope, not even close to 100%. – Nic Nov 16 '18 at 23:36
  • 5
    @NicHartley - However, since the same article states that 90 to 95% of all polio infections are asymptomatic, and presumably not detected in the populations being discussed, a 1% paralysis rate of overall infections implies a 10 to 20% paralysis rate in diagnosed cases. – WhatRoughBeast Nov 17 '18 at 15:52
  • @WhatRoughBeast I'm assuming there's some test for polio infection, seeing as we have numbers for asymptomatic infection. [This](https://www.cdc.gov/polio/about/) implies stool samples can be used (and can, in fact, infect others, as even asymptomatic carriers are still infected and can still transmit the virus). It would genuinely shock me if there was _no_ other way to test. – Nic Nov 17 '18 at 22:04
  • 4
    @NicHartley - Sure, the tests exist. But for the population currently under discussion (3rd world) it seems most unlikely that anything other than symptomatic infections will be reported. – WhatRoughBeast Nov 17 '18 at 22:17
  • So I would say its not just plausible, its likely? – David says Reinstate Monica Nov 18 '18 at 02:35
  • @WhatRoughBeast Oh, I see what you mean -- yeah, that's certainly a fair point. (My mind was stuck in historical-data mode for some reason, where virtually _every_ child would have been tested, because virtually every child was infected with the virus at some point, and they wanted to track the effectiveness of the vaccine) – Nic Nov 18 '18 at 04:18
  • 4
    Your statement: "A fully vaccinated population would be immune from both types of polio." is slightly stronger than the source "If a population is fully immunized, they will be protected against both vaccine-derived and wild polioviruses." If vaccination is not 100% effective, the population won't be "immune", but it will be protected by herd immunity, making outbreaks much less likely. – Oddthinking Nov 19 '18 at 13:54
  • 1
    It is worth to note that some polio cases come from misuse of the vaccine, too. A personal anecdote - my first cousin contracted polio from a vaccine because his mother misled the vaccination doctors and didn't disclose his immunity issues. She was explicitly told by her son pediatrician to _not_ proceed with the vaccination until those issues were solved, and she ignored the warning. He was one of the last cases of Polio in Brazil - the country is free from the disease for almost 30 years, now. – T. Sar Nov 19 '18 at 14:52
  • 2
    @NicHartley I rather doubt every child was tested for polio, given the expense. A seroconversion rate for polio could be extrapolated from a large random sample, especially one not limited to a particular geographic area. Same for measles, where 95% of the population showed evidence of exposure, but clinical cases were far less, even in epidemics. – Andrew Lazarus Nov 19 '18 at 23:03