Polio Vaccine Caused Mutated Virus Outbreak in Nigeria

[emma1325]

http://news.yahoo.com/s/ap/20090814/..._polio_nigeria

Wow. Wow. Wow.

WHO admitting vaccines are causing major problems? WTH is going on?

Great article. Here's a clip, but read the whole thing!


"...Nigeria and most other poor nations use an oral polio vaccine because it's cheaper, easier, and protects entire communities.

But it is made from a live polio virus — albeit weakened — which carries a small risk of causing polio for every million or so doses given. In even rarer instances, the virus in the vaccine can mutate into a deadlier version that ignites new outbreaks.

The vaccine used in the United States and other Western nations is given in shots, which use a killed virus that cannot cause polio.

So when WHO officials discovered a polio outbreak in Nigeria was sparked by the polio vaccine itself, they assumed it would be easier to stop than a natural "wild" virus.

They were wrong..."

[ema-adama]

I know. There are documented cases of the vaccine mutated strain of polio in Argentina and India amounst other countries. In fact I remember there being some concern here on this board that wild polio was making come back until it was clarified that the said child in Argentina had been vaccinated and also was immune compromised.

http://www.mothering.com/discussions...olio+argentina

[keljo05]

i like how further down in the article it says:

Until a better vaccine is ready, WHO and U.S. CDC officials say the oral vaccine is the best available tool to eradicate polio and that when inoculation rates are nearly 100 percent it works fine.

"Nigeria is almost a case study in what happens when you don't follow the recommendations," Kew said.

how nice that they conveniently forget that the vaccine started this.

[kiara7]

But in rare instances, as the virus passes through unimmunized children, it can mutate into a strain dangerous enough to ignite new outbreaks, particularly if immunization rates in the rest of the population are low.

Did you guys notice that? Unimmunized are at fault. Why would the virus need to evolve in unimmunized???

[ema-adama]

Originally Posted by kiara7

Did you guys notice that? Unimmunized are at fault. Why would the virus need to evolve in unimmunized???

I have been trying to figure this out myself.

This study seems to indicate concern about a mutated form of polio emerging in a highly vaccinated population.

Conclusions: Our findings, which show that OPV is excreted for a significant period by children with high humoral immunity, emphasize the long-term potential threat from VDPV in highly vaccinated populations. An adequate immunization program, combined with environmental surveillance, is necessary to prevent poliomyelitis and community transmission of poliovirus.

It seems the virus mutates in the gut of immune compromised people.

Prolonged enteral replication, evolution, and shedding of poliovirus by immunodeficient patients should be considered in the poliovirus eradication strategy. Copyright 1999 Academic Press.

http://www.ncbi.nlm.nih.gov/pubmed/1...?dopt=Abstract

[maxwill129]

My newspaper said in 2008 there were 62 cases of polio...out of a population of about 148,000,000. I would be devastated if my child were among those 62, but I guess I don't get why vaccinate when the chances are really small that one would get polio? Is there something I'm missing?

[ema-adama]

What I do not understand about the virus mutating in unvaccinated guts, is that that is one of the 'advantages' of OPV, is that it spreads in the community, creating immunity even in children who have not received the OPV themselves. And that it stops circulation of polio in the community. Is the hole in this theory that every child has to have the vaccine drops themselves? How many times is enough? Surely every child who gets OPV for the first time is at risk of developing and shedding vaccine derived polio virus? Or is it only if you acquired the virus from a child who had the OPV and you yourself have not had the vaccine itself?

I think that this issue of it mutating in unvaccinated guts is not the real issue - the real issue is that the virus is able to mutate back to it's neurovirulent self in the guts of some people and has the potential to infect. I wonder what conditions optimise mutation?

How can they even tell if a child who develop AFP has a virus that mutated in their own gut or the gut of another child/person?

The more I read about it, the more it seems that immune compromised guts are where the virus mutates and health officials are assuming that higher vaccination rates will prevent this, when it is the vaccine iteself that is creating the concern. I am sure there are calls for a better vaccine on the horizon.

http://www.pubmedcentral.nih.gov/art...i?artid=533926 Goes into the mutation of polio virus in the gut. With much discussion on the virus mutating in the guts of immune compromised individuals.

Anyone who can help me understand just how this works, I really would like to understand.

[carriebft]

The reason it evolves in unimmunized kids mostly is that the vaccine is pretty highly effective. When the vaccine strain gets out, they usually find it mutated in kids who have not gotten the vaccine themselves. (which is why they blame that I guess).

[carriebft]

You also have to note Nigeria's history with vaccine as part of this...what happened when they stopped and how that affects this problem today. kwim?

[emma1325]

Originally Posted by carriebft

You also have to note Nigeria's history with vaccine as part of this...what happened when they stopped and how that affects this problem today. kwim?

Well, jumping off from their refusal of the vaccine and the resulting increased cases of polio, I wonder what could have been done differently besides going back in with the vaccine which is known to mutate? I'm thinking a campaign to improve nutrition and water sanitation would have been safer and more appropriate than a vaccine program which carried pretty serious risks.

[caned & able]

Originally Posted by carriebft

You also have to note Nigeria's history with vaccine as part of this...what happened when they stopped and how that affects this problem today. kwim?

Does Nigeria use DDT? They do have a malaria problem.

DDT has been associated with childhood paralysis.

[carriebft]

Originally Posted by emma1325

Well, jumping off from their refusal of the vaccine and the resulting increased cases of polio, I wonder what could have been done differently besides going back in with the vaccine which is known to mutate? I'm thinking a campaign to improve nutrition and water sanitation would have been safer and more appropriate than a vaccine program which carried pretty serious risks.

There are quite a few such programs working in Nigeria:

http://www.wateraid.org/nigeria/default.asp

http://www.cbn.com/cbnnews/world/200...eria-Villages/

http://www.unicef.org/infobycountry/nigeria_50616.html

..etc

But I guess I feel that a mixed approach is going to be needed.

[caned & able]

But those irrigation and sanitation programs do not get the credit for success that the vaccines get in the end. So which really works for the benefit of the community...the sanitation or the vaccines or a combination of both?

[ema-adama]

Originally Posted by carriebft

The reason it evolves in unimmunized kids mostly is that the vaccine is pretty highly effective. When the vaccine strain gets out, they usually find it mutated in kids who have not gotten the vaccine themselves. (which is why they blame that I guess).

Ok, but does that mean the virus mutated in the gut of an unvaccinated child, or that the child contracted a VDPV?
What does that mean about the assuptions made that OPV contributes to community immunity by dispersing throughout the community?

I honestly think that by pointing the finger at unvaccinated children the point is missed. I have not read anything about the virus mutating in unvaccinated guts, and I have read quite a bit about the virus mutating in vaccinated immune compromised individuals.

ETA: do you have any reading material on the incidence of VDPV in vaccinated and unvaccinated children?

[Jugs]

^^Ditto. Viruses mainly mutate as a survival mechanism, in an attempt to bypass immunological and antiviral efforts; it doesn't make sense for the unvaccinated to be the petri dish for viral mutation when they can host the virus in its un-mutated state.

[ema-adama]

Is there no science to support the claim that unvaccinated guts are the cause of these mutations?

[carriebft]

http://www.academicjournals.org/sre/...%20et%20al.pdf

(the article itself and lots of its citations are useful here. pages 409-415 are especially relevant)

[ema-adama]

Thanks Carrie,

In summary: OPV seems to offer immunity to VDPV's. However OPV itself can cause paralysis. So, when the wild virus is no longer in circulation, there is the plan to stop OPV. However, it seems unlikely that they can stop administering OPV as there are now VDPV's in circulation, and immune compromised vaccinated individuals can actually shed these VCPV's for many years.Introducing IPV in developing countires is too large of a project. OPV can be administered by a volunteer and requires no special training. IPV is a whole other ballgame.

This whole debate has very little to do with countries that have eradicated polio from what I can understand. And it certainly has nothing to do with the politics of vaccinating in the developed world. It's about how to manage polio in Developing Countries. Although I did not read about IPV protecting against VDPV's from the OPV, I am sure the authorities who plan all of this would not endager the health of children so indescriminantly.

[Pirogi]

First, my disclaimer is that I have not been researching this for very long, so please don't if I muss it up a bit. Please do correct me.

First, a bit of definition is in order. From this study published earlier, there are three categories of poliovirus isolates, and they are defined by the percentage of genetic divergence (mutation) from the corresponding Sabin OPV strain.

1. OPV-like virus: <1% divergent
2. VDPVs: 1-15% divergent
3. WPVs: >15% divergent (by the way, does this mean that a strain that has replicated for 15 years that originated from OPV becomes reclassified as "wild"?)

That same article and this Global Polio Eradication Initiative site further defines and divides VDPVs into three categories:

1. iVDPVs (immunodeficiency-related vaccine-derived poliovirus): isolated from persons with primary immunodeficiencies who have prolonged VDPV infection after exposure to OPV
2. cVDPVs (circulating vaccine-derived poliovirus): associated with sustained person-to-person transmission and considered to be circulating in the environment/community, resulting in more than one patient with paralysis
3. aVDPVs (ambiguous vaccine-derived poliovirus): isolated from a single immunocompetent AFP or paralytic poliomyelitis patient with or without additional isolates from contacts, or from healthy individuals or the environment in absence of paralytic cases.

Also, it is important that the generally accepted "normal" genome mutation rate is 1% per year, although this article posted earlier indicates that the virus can replicate faster than that. This is important because this set rate of evolution inherently means that cVDPV has been replicating and evolving for at least a year after an OPV dose by the time it is discovered. The accepted "normal" virus replication period is 4-6 weeks after the dose.

By definition, virus that has come directly from a primary-immunocompromised person is iVDPV. Also by definition, cVDPV is the automatic label if there is an outbreak of non-WPV in the community. All the head-scratchers are labeled aVDPV. Statistically, VDPV outbreaks occur where immunization rates are low (below 95%). So IMO, it is a bit of sleight of hand that unimmunized children are "blamed" as the replication vehicles for cVDPV. I have seen no evidence that OPV only replicates and mutates in unimmunized children.

The folks at the Global Polio Eradication Initiative insist that,

More importantly, no iVDPV has been observed to transmit or spread to others. For this reason, the public health significance of 'chronic iVDPV excretors' is different when compared to circulating VDPVs. However, iVDPVs may pose an increasing risk as the world moves towards the eventual cessation of OPV use.

I think the key word there is "observed." The fact that there exist (a few known) immunodeficient people and immunocompetent people (including the two in this study and this study posted earlier) who have been found to excrete virus in the 1-15% mutation range for months or years proves that it is at the very least possible that a person (immunocompromised or not) who receives OPV is capable of hosting a mutating virus, which could be transmitted to others. I would argue that since usually at least 85% of the population where the outbreak has occurred is vaccinated with OPV, statistically it may be more likely that VDPV mutated in the vaccinated person than in the unvaccinated one.

The only way to be sure that a person receiving OPV is not "responsible" when cVDPV emerges is to test the stool of every person who receives OPV, isolating and destroying each infected stool produced by each person until that person stopped shedding virus. I am positive that each and every stool of each and every person who has ever received the OPV has NOT been tracked and controlled, so it is exceedingly foolish for any organization to claim or imply that unimmunized people are the sole host during replication, or that iVDPV is not responsible for community outbreaks.

Then again, the idea of blame when it comes to infectious disease is ridiculous to me. We will never, ever "win" against it. No reason to blame anyone. But, that is another post ...