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This study from 2018 establishes a strong correlation between the introduction of a new version of a polio vaccine in 2005 in India and a very high number of Non-Polio Flaccid Acute Paralysis (NPAFP) cases:

Analysis of data over 10 years (from 2000 to 2010) showed that the NPAFP rate increased nationally during this time [12]. The NPAFP rate in 2010 was 12/100,000, which was some way away from the expected number of 2/100,000. It has been reported that in 2005 there was a sharp increase in the national NPAFP rate, which coincided with the introduction of a high-potency monovalent vaccine that contained 5 times the number of Type 1 viruses, compared to that contained in the previously used vaccine [13]. The NPAFP rate, which was 3.11/100,000 in 2004, more than doubled (to 6.43/100,000) in 2005.

While the number of NPAFP cases started dropping along with the number of doses of vaccine administered, the authors can't establish a causal link and don't question the necessity of the vaccination campaign, but recommend to keep lowering the number of doses now that the disease has pretty much been eradicated.

This previous study from 2013 actually goes further and says the correlation is strong enough to suspect a causal link

The incidence of NPAFP was strongly associated with the number of OPV doses delivered to the area. A dose–response relationship with cumulative doses over the years was also observed, which strengthens the hypothetical relationship between polio vaccine and NPAFP. The fall in the NPAFP rate in Bihar and UP for the first time in 2012, with a decrease in the number of OPV doses delivered, is evidence of a causative association between OPV doses and the NPAFP rate.

Based on the number of polio cases in India at the time (less than 1,000 a year, figure 2 of this other study) and the excess number of NPAFP cases (490,000 over 12 years - table 2 of the first study), can we safely say that the "high potency" version of the vaccine introduced in 2005 ended up having dire detrimental effects? If so, were there legitimate reasons for the change of vaccine? If not, what could be a plausible cause of the unusually high number of NPAFP cases?

Jukurrpa
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    I feel the need to indicate that I'm by no means anti vaccines, far from it, but "without the freedom to criticize, there is no true praise" - Pierre Beaumarchais – Jukurrpa Jun 01 '20 at 19:13
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    Your title makes it look like the new vaccine is worse that having polio spread unchecked ("worse than the disease") whereas the claim in the paper is that the new vaccine is worse than the old vaccine. – DJClayworth Jun 01 '20 at 19:19
  • Good point, I updated the title – Jukurrpa Jun 01 '20 at 19:23
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    [An earlier study](https://pediatrics.aappublications.org/content/135/Supplement_1/S16.2) pointed out this correlation in 2015 and explicitly argued for a causal relationship. I'm not finding any direct critiques of this study. – Brian Z Jun 01 '20 at 19:57
  • Thanks @BrianZ , added it to the question. Also edited the title again to be more straightforward. – Jukurrpa Jun 02 '20 at 08:49
  • The title still reads "needlessly", and the body "unnecessary". That is asking for judgement on what actually happened vs. what might have happened, which we usually don't do here. The idea is to *erradicate* polio once and for all, something humanity is [on the brink of achieving](https://skeptics.stackexchange.com/a/42805/25415). Even *if* the vaccine was responsible for the NPAFP case increase -- which the studies left at *hypothetical* -- it is still quite a leap to call the 2005 vaccine "unecessary". What were the reasons for introducing it? And what is "dire"... (t.b.c.) – DevSolar Jun 02 '20 at 10:34
  • (ctd.) ...when better vaccines are being used since, and the outlook is that the disease, and with it the need for vaccination, might go away completely in the forseeable future? There's much room for "opinion-based" here; what, exactly, are the *facts* you are looking for? – DevSolar Jun 02 '20 at 10:39
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    The question is about the version of the vaccine that was introduced in 2005, not the need to vaccinate against polio. I don't think it is opinion-based to try to figure out whether this change of vaccine was needed considering that polio was already disappearing with the previous version of the vaccine (again, less than 1,000 cases a year) and that two studies strongly suspect the new vaccine of having caused close to half a million cases of paralysis. – Jukurrpa Jun 02 '20 at 11:50
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    @Jukurrpa: So you feel the people introducing that vaccine type in 2005 should have known from the 2013 study that its use would correlate with an increase of NPAFP? I'm blowing the horn here because your choice of words shows, to me, that you have a premeditated opinion on this. You've got one side of the story. Are you at all interested in hearing the other (i.e., the reason for the change in vaccine makeup, and/or whether it was *causative* for the increase in NPAFP, and/or it could have been *foreseen*) -- or are you just looking for people agreeing with you ("push question")? – DevSolar Jun 02 '20 at 17:17
  • I currently have an opinion on this because both studies linked in the question strongly suspect that the 2005 vaccine might have caused harm. But this opinion is not definitive because I'm missing information. I'd be more than happy to change my mind if I read that the NPAFP cases had a different reason, or that there were legitimate reasons to introduce a new, unproven vaccine. This is why I asked the question in the first place. It might sound loaded, but that's because the currently available information strongly points in this direction. Feel free to suggest an edit though! – Jukurrpa Jun 02 '20 at 18:35
  • On a side note: "So you feel the people introducing that vaccine type in 2005 should have known from the 2013 study that its use would correlate with an increase of NPAFP?" If the causal link was recognized, there is a way of asking essentially the same question without making it sound stupid: "Should these people have been more cautious before introducing a new vaccine, at scale, for a disease already on the brink of extinction?". I don't think asking this question would be a crazy idea. – Jukurrpa Jun 02 '20 at 18:37
  • Your new title also introduces a judgement, "needlessly", which the studies don't claim. – DJClayworth Jun 02 '20 at 21:06
  • @DJClayworth [Any iatrogenic damage that could be avoided *is* 'needless', if not often a stronger word might need to be used.](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1124014/) But I agree insofar that any adjective/adverb will carry 'a judgement' here, and that the title works just deleting that one word (while reducing the implicit comparison to prior, though). Then we arrive at "cause" which will be cited as reason for contention here… – LangLаngС Jun 03 '20 at 11:34
  • Ok, I removed needless from the title and added a follow-up question in case the causal link is established. – Jukurrpa Jun 03 '20 at 13:30
  • @Jukurrpa: Still asking for a judgement call between reasons for changing the vaccine (that aren't yet established here), and consequences that weren't apparent until years afterwards. The first question to answer would be, "**why** was a new polio vaccine introduced in 2005", and then build up from there. You want conclusions to be drawn for a not-yet-established fact base... – DevSolar Jun 03 '20 at 13:41
  • The "why"(or "legitimate reason") is irrelevant and yet easily answered: "someone said 'better', others believed it, *now* we see(?!?)". Whether this 'better cost/benefit relation' is indeed 'less adverse outcomes', 'more positive outcomes as lowered disease burden' or just things like 'increased profits' 'easier administration' is not that interesting *on this site?* (But interesting tangential info in an A) So, currently, third-to-last Q in body is the main and good one? ~"Was the newer vaccine indeed responsible for a worse risk/benefit ratio than the old?" – LangLаngС Jun 03 '20 at 14:40
  • @LаngLаngС: Well, to judge that you need to know what the benefits -- i.e., the why -- for that new vaccine *were*, don't you? And then you'd still be in "opinion-based" territory... – DevSolar Jun 03 '20 at 14:41
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    It should be noted that the vaccine being used in India is apparently a "live virus" version (a la Sabin), vs a "killed virus" (Salk) vaccine. Such live virus vaccines are known to cause a cause a certain (hopefully small) number of (hopefully mild) cases of acute polio infection. (This is why the use of the Sabin vaccine has been largely discontinued in the US and most other "1st world" countries.) The live virus vaccine is often used in other countries, however, because it's easy to administer and it tends to create better "herd immunity". – Daniel R Hicks Jun 03 '20 at 17:51
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    @DanielRHicks Second this. In high risk areas the live vaccine prevents more cases than it causes and thus is the vaccine of choice. In low risk areas the downside isn't worth it, the killed vaccine is used even though it is not as effective. – Loren Pechtel Jun 06 '20 at 04:20

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