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> if you give the vaccine, then the vaccine causes more cases (of type 2) than it's stopping. > There's no solution here - either option makes things worse.

by yholio 5y ago

> if you give the vaccine, then the vaccine causes more cases (of type 2) than it's stopping. > There's no solution here - either option makes things worse. That's false and misleading. The OPV2 vaccine will stop both vaccine-derived cvdpv2 virus from spreading and the wild type 2, which has been eradicated. Since OPV2 is a live attenuated virus, it will also continue to multiply and confer protection to any person drinking contaminated water, the vaccine "spreads". It is thus highly effective at stopping polio and in no way it can be said that it "causes more cases than it's stopping". The problem with OPV2 is that it has a relatively higher chance of reverting to an variant that causes polio. This is not a problem if the population has a high level of vaccination, since the live attenuated virus cannot propagate and mutate. It's only problematic in low coverage areas where it can multiply extensively in many hosts. Thus, the cvdpv2 epidemic is an expression of low vaccination rates, similar in every way to a wild poliovirus resurgence. The novel OPV2 vaccine will improve the genetic stability of the attenuated virus, allowing further "viral vaccinations" in low coverage areas - but we could eradicate cvdpv2 today with the existing OPV2 vaccine, if only we could get good vaccinations rates everywhere, as it has happened in most of the world.

ars 5y ago
You are completely misinformed about this. I spent quite a long time reading about this. What you write is what they hoped would happen. However it did NOT happen. The reason is that the more you try to vaccinate the entire population, the more cases of cvdpv2 you cause. Until you hit that magic 100% you cause more harm than you prevent. And in the real world 100% is impossible. So yes opv2 "causes more cases than it's stopping" - there are zero cases of wild type 2, so it's stopping nothing except itself. And in fact that people running this campaign noticed this and stopped vaccinating with opv2! (Which perhaps you did not know.) The new version of it will hopefully help, and we can eradicate this. But right now Polio eradication is failing, not because of Taliban, but because of cvdpv2. I have high hopes for the new version, but it'll be years before we know.
- yholio 5y ago
  > The reason is that the more you try to vaccinate the entire population, the more cases of cvdpv2 you cause. Until you hit that magic 100% you cause more harm than you prevent. This makes little sense if you understand that both wpv2 and cvdpv2 were eliminated in the poorest regions of the world using OPV2. If what you claim is true, elimination would have been impossible, you would simply replace wpv2 with cvdpv2, since any attempt at eradication would seed new cvdpv2 cases. Inactivated injectable vaccine, which does not boost herd immunity, is inefective in these countries with limited health systems. > And in fact that people running this campaign noticed this and stopped vaccinating with opv2! (Which perhaps you did not know.) Perhaps you refer to the global coordinated action to move from trivalent vaccine to bivalent (wpv1+ wpv3) in 2016 after the wild type 2 virus was certified as eradicated. But monovalent OPV2 was still being used recently to target specific areas where cvdpv2 is endemic. It makes little sense to use it elsewhere and seed cvdpv2.
  - ars 5y ago
    And 8 years later the vast majority of Polio in the world is cvdpv2. (There is more cvdpv2 then wild type 1 and 3 combined.) You are correct in your details, but are completely missing the bigger picture. If you look at stats there is zero evidence that cvdpv2 is going away, it just shifts countries, goes up, goes down, but has no signs of ending. If not for the new vaccine (and I hope it works), cvdpv2 indicates the failure to eradicate Polio. The new vaccine may change the picture, we shall see in about 2 years. Right now the Taliban is not the biggest obstacle to Polio eradication, cvdpv2 is. And if you check my comments this has been my claim from the start, so I'm not sure what you are arguing against. Just because vaccines are great, doesn't mean they are perfect, it's not necessary to reflexively defend them.
    - akamaka 5y ago
      I think you’re being overly dramatic. There have been dozens of cVDPV outbreaks that have been successfully contained in countries around the world. We know how to do it even with our existing vaccines. These outbreaks don’t just come and go at random, they happen in places with inadequate vaccination and are eliminated using a proven playbook. New vaccines will make the process smoother and faster, but we’re certainly not at a dead end without them.

by yholio 5y ago

ars 5y ago

You are completely misinformed about this. I spent quite a long time reading about this. What you write is what they hoped would happen. However it did NOT happen. The reason is that the more you try to vaccinate the entire population, the more cases of cvdpv2 you cause. Until you hit that magic 100% you cause more harm than you prevent. And in the real world 100% is impossible. So yes opv2 "causes more cases than it's stopping" - there are zero cases of wild type 2, so it's stopping nothing except itself. And in fact that people running this campaign noticed this and stopped vaccinating with opv2! (Which perhaps you did not know.) The new version of it will hopefully help, and we can eradicate this. But right now Polio eradication is failing, not because of Taliban, but because of cvdpv2. I have high hopes for the new version, but it'll be years before we know.

yholio 5y ago
> The reason is that the more you try to vaccinate the entire population, the more cases of cvdpv2 you cause. Until you hit that magic 100% you cause more harm than you prevent. This makes little sense if you understand that both wpv2 and cvdpv2 were eliminated in the poorest regions of the world using OPV2. If what you claim is true, elimination would have been impossible, you would simply replace wpv2 with cvdpv2, since any attempt at eradication would seed new cvdpv2 cases. Inactivated injectable vaccine, which does not boost herd immunity, is inefective in these countries with limited health systems. > And in fact that people running this campaign noticed this and stopped vaccinating with opv2! (Which perhaps you did not know.) Perhaps you refer to the global coordinated action to move from trivalent vaccine to bivalent (wpv1+ wpv3) in 2016 after the wild type 2 virus was certified as eradicated. But monovalent OPV2 was still being used recently to target specific areas where cvdpv2 is endemic. It makes little sense to use it elsewhere and seed cvdpv2.
- ars 5y ago
  And 8 years later the vast majority of Polio in the world is cvdpv2. (There is more cvdpv2 then wild type 1 and 3 combined.) You are correct in your details, but are completely missing the bigger picture. If you look at stats there is zero evidence that cvdpv2 is going away, it just shifts countries, goes up, goes down, but has no signs of ending. If not for the new vaccine (and I hope it works), cvdpv2 indicates the failure to eradicate Polio. The new vaccine may change the picture, we shall see in about 2 years. Right now the Taliban is not the biggest obstacle to Polio eradication, cvdpv2 is. And if you check my comments this has been my claim from the start, so I'm not sure what you are arguing against. Just because vaccines are great, doesn't mean they are perfect, it's not necessary to reflexively defend them.
  - akamaka 5y ago
    I think you’re being overly dramatic. There have been dozens of cVDPV outbreaks that have been successfully contained in countries around the world. We know how to do it even with our existing vaccines. These outbreaks don’t just come and go at random, they happen in places with inadequate vaccination and are eliminated using a proven playbook. New vaccines will make the process smoother and faster, but we’re certainly not at a dead end without them.