4 ms·

They kind of had to stop downplaying the importance of vaccine-derived polio. Apparently it's now the main form of polio actually paralyzing kids at this point

by makomk 7y ago

They kind of had to stop downplaying the importance of vaccine-derived polio. Apparently it's now the main form of polio actually paralyzing kids at this point in the campaign to eradicate the disease, and no-one seems to have any workable end-game: https://www.npr.org/sections/goatsandsoda/2019/11/15/779865471/polio-vaccine-may-be-preventing-the-end-of-polio?t=1575755256060 https://www.npr.org/sections/goatsandsoda/2019/11/15/7798654... Western countries eradicated polio thanks to better sewage and water treatment limiting the spread of vaccine-derived strains and a switch to an injectable dead vaccine that's less effective but can't cause disease outbreaks, neither of which seem to be feasible in the affected countries at this time. Stopping the outbreaks is done using mass vaccinations which introduce more vaccine poliovirus into circulation, causing more outbreaks down the line. Also, it seems the claim in the article that type 2 poliovirus has been eliminated isn't quite the whole truth. Wild type 2 poliovirus has been eliminated, but vaccine-derived versions of it are still in circulation and causing paralysis.

ars 7y ago
The good news there is that vaccine derived versions don't seem to circulate for very long. So if you can eradicate the wild type, stop immunizing with the vaccine type, within a year or two it should be gone.
- makomk 7y ago
  Other way around, as I understand it: once the vaccine-derived strains have been circulating for a year or so, they become every bit as virulent and dangerous as the original wild polio and remain that way indefinitely unless they're stamped out using vaccination. The only way we can tell they're vaccine-derived rather than wild at that point is by using genetic sequencing to trace their heritage since they're otherwise exactly like wild polio. If we could somehow ensure that the vaccine strains didn't circulate for so long they wouldn't be able to regain their virulence and we wouldn't have this problem, but that's easier said than done.
selimthegrim 7y ago
There is a big scandal right now in Pakistan where vaccine was improperly stored and given to kids causing VDP and the guy in charge of eradication tried to cover it up and was forced to resign.
- gus_massa 7y ago
  Do you have a link for this? Preferably one with the technical info. The problem with a bad storage of the vaccine is that it makes it ineffective. I guess if the storage is very bad, some bacteria may grow in the vial (???), but it would not cause VDP. In the injectable version, the virus is totally "dead", so whatever you do, it would not cause VDP. In the oral version, the virus is "alive". If the storage is bad it may destroy the virus making the vaccine ineffective. But the virus can't reproduce and mutate inside the vial to become dangerous. The virus need approximately one year and a bunch of host to mutate and get dangerous. So, whatever crappy storage they used, the vaccine can't give the kid VDP. The problem may be that a bad storage may make all the vaccination campaign ineffective, you think that you have 99% of the population vaccinated, but the effective number is much smaller. In that case the virus from the vaccine can spread and mutate and cause problems later after a few hops in the unvaccinated kids.
  - selimthegrim 7y ago
    https://www.theguardian.com/global-development/2019/nov/07/pakistan-accused-of-cover-up-over-fresh-polio-outbreak https://www.theguardian.com/global-development/2019/nov/07/p... https://www.dawn.com/news/1515632 https://www.dawn.com/news/1515632
    - gus_massa 7y ago
      Thanks for the links. The relevant paragraph from the first article is: > After the strand was eliminated from Pakistan five years ago, all P2 vaccines should have been collected from hospitals and clinics and not used. However, it appears a P2 vaccine was administered accidentally and a child became a carrier for the disease. Tests on the new cases allegedly show the children are all carrying a vaccine-derived form of the disease. When they switched from the vaccine with all the variants to the oral vaccine without P2, did they continue using the inyectable version with all the variants as recommended by WHO?
wbl 7y ago
The biggest polio epidemic in the US happened in 1950's NYC. Sewage and water treatment are not enough to stop polio spreading. They also eliminated type 2 from the oral vaccine.

by makomk 7y ago

ars 7y ago

The good news there is that vaccine derived versions don't seem to circulate for very long. So if you can eradicate the wild type, stop immunizing with the vaccine type, within a year or two it should be gone.

makomk 7y ago
Other way around, as I understand it: once the vaccine-derived strains have been circulating for a year or so, they become every bit as virulent and dangerous as the original wild polio and remain that way indefinitely unless they're stamped out using vaccination. The only way we can tell they're vaccine-derived rather than wild at that point is by using genetic sequencing to trace their heritage since they're otherwise exactly like wild polio. If we could somehow ensure that the vaccine strains didn't circulate for so long they wouldn't be able to regain their virulence and we wouldn't have this problem, but that's easier said than done.

selimthegrim 7y ago

There is a big scandal right now in Pakistan where vaccine was improperly stored and given to kids causing VDP and the guy in charge of eradication tried to cover it up and was forced to resign.

gus_massa 7y ago
Do you have a link for this? Preferably one with the technical info. The problem with a bad storage of the vaccine is that it makes it ineffective. I guess if the storage is very bad, some bacteria may grow in the vial (???), but it would not cause VDP. In the injectable version, the virus is totally "dead", so whatever you do, it would not cause VDP. In the oral version, the virus is "alive". If the storage is bad it may destroy the virus making the vaccine ineffective. But the virus can't reproduce and mutate inside the vial to become dangerous. The virus need approximately one year and a bunch of host to mutate and get dangerous. So, whatever crappy storage they used, the vaccine can't give the kid VDP. The problem may be that a bad storage may make all the vaccination campaign ineffective, you think that you have 99% of the population vaccinated, but the effective number is much smaller. In that case the virus from the vaccine can spread and mutate and cause problems later after a few hops in the unvaccinated kids.
- selimthegrim 7y ago
  https://www.theguardian.com/global-development/2019/nov/07/pakistan-accused-of-cover-up-over-fresh-polio-outbreak https://www.theguardian.com/global-development/2019/nov/07/p... https://www.dawn.com/news/1515632 https://www.dawn.com/news/1515632
  - gus_massa 7y ago
    Thanks for the links. The relevant paragraph from the first article is: > After the strand was eliminated from Pakistan five years ago, all P2 vaccines should have been collected from hospitals and clinics and not used. However, it appears a P2 vaccine was administered accidentally and a child became a carrier for the disease. Tests on the new cases allegedly show the children are all carrying a vaccine-derived form of the disease. When they switched from the vaccine with all the variants to the oral vaccine without P2, did they continue using the inyectable version with all the variants as recommended by WHO?

wbl 7y ago

The biggest polio epidemic in the US happened in 1950's NYC. Sewage and water treatment are not enough to stop polio spreading. They also eliminated type 2 from the oral vaccine.