4 ms·

A lot of the news coverage dances around the issue, but the direct cause of this actually seems to be a catastrophically failed attempt to switch away from the

by makomk 4y ago

A lot of the news coverage dances around the issue, but the direct cause of this actually seems to be a catastrophically failed attempt to switch away from the previous polio vaccine. Vaccine-derived poliovirus outbreaks used to be pretty rare because the vaccine kept them under control, but there was always the fear that some war or other disruption to vaccination would trigger a major outbreak. So the WHO came up with a plan: everyone around the world would stop using oral polio vaccines with the type 2 poliovirus components (which is the main culprit and protects against a variant that's been eradicated in the wild), they'd estroy all their old trivalent vaccines and switch to bivalent type 1 and 3 ones, any outbreaks of vaccine-derived poliovirus would be mopped up with a special type 2 only vaccine reserved for that purpose, and then it'd be gone for good. Instead vaccine-derived poliovirus outbreaks exploded all over the world. The nOPV2 vaccine was then rushed out through development and into production to try and patch up the mess. (In theory they could've just switched back to the old vaccine temporarily, but that would mean admitting failure and besides they didn't have the big stockpiles of it anymore.)

lucb1e 4y ago
To be sure I understood correctly, it sounds like the WHO's plan was a good one, given the information available and outlook at the time, and it had a good chance of success, except the low chance of failure materialized? (Aside from the part where they avoided admitting defeat afterwards, although given "and besides they didn't have the big stockpiles of it anymore" it wouldn't have been a solution anyhow.)
- akira2501 4y ago
  They introduced a real vulnerability throughout the entire system to deal with a perceived future vulnerability in part of the system. It might have been a good idea, depending on the details of the outlook at the time.. but the plan itself was a compromise and possibly not a particularly well modeled or tested one.
JumpCrisscross 4y ago
> a catastrophically failed attempt to switch away from the previous polio vaccine There are broadly two types of polio vaccines: the kind that inoculates the gut (OPV), taken orally, and the kind that inoculates in the blood (IPV), administered intravenously [1]. (the "I" stands for inactivated.) Both prevent polio, the disease. But only the former is sterilizing, i.e. keeps you from spreading poliovirus. It is also, unfortunately, the one that can leave the vaccinated person's gut to infect someone who is unvaccinated. So if you have a polio outbreak in a vaccine-deficient population, administering non-sterilizing vaccine will keep those people unparalyzed. But it will do nothing to stop the spread. The sterilizing vaccine will help stop the spread. But at the cost of introducing vaccine-derived polio into the mix. We had the luxury of using only the non-spreading, non-sterilizing vaccine in America. That's the benefit of elimination: you can switch to the lower-risk version. It does not seem that we were able to keep it. [1] https://en.wikipedia.org/wiki/Polio_vaccine https://en.wikipedia.org/wiki/Polio_vaccine

by makomk 4y ago

lucb1e 4y ago

To be sure I understood correctly, it sounds like the WHO's plan was a good one, given the information available and outlook at the time, and it had a good chance of success, except the low chance of failure materialized? (Aside from the part where they avoided admitting defeat afterwards, although given "and besides they didn't have the big stockpiles of it anymore" it wouldn't have been a solution anyhow.)

akira2501 4y ago
They introduced a real vulnerability throughout the entire system to deal with a perceived future vulnerability in part of the system. It might have been a good idea, depending on the details of the outlook at the time.. but the plan itself was a compromise and possibly not a particularly well modeled or tested one.

JumpCrisscross 4y ago

> a catastrophically failed attempt to switch away from the previous polio vaccine There are broadly two types of polio vaccines: the kind that inoculates the gut (OPV), taken orally, and the kind that inoculates in the blood (IPV), administered intravenously [1]. (the "I" stands for inactivated.) Both prevent polio, the disease. But only the former is sterilizing, i.e. keeps you from spreading poliovirus. It is also, unfortunately, the one that can leave the vaccinated person's gut to infect someone who is unvaccinated. So if you have a polio outbreak in a vaccine-deficient population, administering non-sterilizing vaccine will keep those people unparalyzed. But it will do nothing to stop the spread. The sterilizing vaccine will help stop the spread. But at the cost of introducing vaccine-derived polio into the mix. We had the luxury of using only the non-spreading, non-sterilizing vaccine in America. That's the benefit of elimination: you can switch to the lower-risk version. It does not seem that we were able to keep it. [1] https://en.wikipedia.org/wiki/Polio_vaccine https://en.wikipedia.org/wiki/Polio_vaccine