> 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.
> 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.