[ars]

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]

> 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]

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]

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.

[ars]

I feel like you keep missing the point. Why are there still outbreaks 6 years later? (Answer: Because we keep causing the outbreaks.)

Is the plan to just keep vaccinating forever? Doesn't that mean that eradication failed? Wild type 2 is extinct, so why are we still fighting it? (Answer: Because we are fighting our own actions.)

> We know how to do it even with our existing vaccines.

You sure? Because it sure doesn't look like success from here.

> they happen in places with inadequate vaccination

If that were true why the switch to bivalent? How can you have "adequate" vaccination when we are not even vaccinating in the first place?

> and are eliminated using a proven playbook.

That's exactly the problem - they do not get eliminated. All we are doing is keeping outbreaks from getting huge, by creating small outbreaks.

This new vaccine is a complete game changer, not the incremental step you think it is.

[akamaka]

Where did you get these outlandish expectations of how much progress would have been made by now? The plan, above all else, was and is to eliminate wild polio virus. Even in the best case scenario, we’re still 5-10 years away from being able to declare it extinct, so you should expect the OPV is still going to be in use until then, and the risks of vaccine-derived polio will still have to be managed for a long time to come. Unfortunately not every country have done a perfect job of that, but it certainly is possible, as demonstrated by the majority of the world having zero cases.

[yholio]

I think 'ars' is leading you into a rhetorical trap. The objective was never eliminating the wild virus, the objective was curing polio. The OPV vaccine is a bit like fighting fire with fire: you burn down the forest (immunize susceptible hosts) in a controlled fashion, so that the forest fire cannot reach homes (paralyze children). But when your house burns down, it's irrelevant if it was the "wild" fire or a fire set by the firefighters, i.e a attenuated virus that mutated.

What 'ars' seems to be missing is that this particular "forest" is very rapidly growing back, in some countries you have in excess of 5% of the population as infants each year. Those are new hosts that were never vaccinated, and due to the extreme contagiousness of the disease a few years of lack of coverage can reignite the fire. What happened after OPV2 withdrawal was that a whole new generation inoculated with only bivalent (type 1+3) vaccine became susceptible to cvdpv2 that was still circulating in small pockets.

Essentially, the campaign failed the end-game strategy, they proved they can reduce the infection to arbitrarily low levels using trivalent OPV, but once you take OPV away, as they attempted for a single strain, the epidemic reignites. It's irrelevant if it's a wpv or cvdpv strain. The end-game was always considered a challenge by experts, but a variety of reasons, Covid, political issues etc. conspired to make it very difficult.

This whole thread leaves me very pessimistic about the prospects of eradication. If a relatively inteligent and educated internet-person that has proper sanitation cannot understand these epidemiological dynamics and claims that "OPV causes more infections than it cures", what's the chance you can explain it to rural farmers, especially after the global rise of the antivax movement after Covid?