What is a vaccine-derived poliovirus?

A vaccine-derived poliovirus (VDPV) is a strain of the weakened poliovirus that was initially included in oral polio vaccine (OPV) and that has changed over time and behaves more like the wild or naturally occurring virus.

https://www.cdc.gov/vaccines/vpd/polio/hcp/vaccine-derived-p...

Notably, this isn't someone reverse engineering polio from vaccines. (it's still endemic so no need)

Although arguably that's exactly what the virus did itself.

If you understand the limitations of the two types of vaccines, this story is just something that should be expected to happen.

Someone traveled from a country where the weakened live version is given to the UK. This live version mutated in that individual to become transmissible (this mutation happens in around one in a million individuals). The UK vaccinates with the non-live version. This non-live version cannot mutate, but it is non-sterilizing- the vaccinated can still become infected in their gut- the vaccine prevents it from getting into their bloodstream and become poliomyelitis. We now we see this outcome in the sewage samples.

It looks it stems from pockets of London inhabited by communities historically resistant vaccination and/or a traveler from a country historically resistant to vaccination who has traveled there.

  UK Health Security Agency (UKHSA) experts
  believe a traveller – likely from 
  Pakistan, Afghanistan or Nigeria - shed
  the virus in their stools after being
  given the oral polio inoculation.[1][2]

  It is likely the virus was shed by someone
  who was recently vaccinated against polio
  in a country where it has not yet been
  eradicated, such as Pakistan, Afghanistan
  or Nigeria.[3]

https://www.the-sun.com/health/5615177/first-outbreak-highly...

[2] National incident declared after polio detected in London sewage

https://www.youtube.com/watch?v=tz7zsLJqZ7M

[3] Traces of polio virus found in London sewage as health officials declare national incident

https://news.sky.com/story/traces-of-polio-virus-found-in-lo...

In the UK as a child you are offered the Polio vaccine. Uptake is around 95% in the UK overall, and 91% in London.

> “Vaccine-derived poliovirus has the potential to spread, particularly in communities where vaccine uptake is lower,” said Dr Vanessa Saliba, consultant epidemiologist at the UKHSA.

https://www.theguardian.com/society/2022/jun/22/polio-uk-pub...

On the plus side, I'm glad to hear London has active sewerage surveillance in place

I understand that the vaccine-derived poliovirus originates from the live/attenuated virus used in the oral vaccine. (Or at least, first-gen versions of it! Does nOPV2 conclusively address these issues?)

Can anyone explain why it's rare for inactivated vaccines to be able to be delivered via the oral route? It would have been a lot more efficient/user-friendly to deliver the Coronavirus vaccinations in this manner, but almost all of the vaccines we seem to use nowadays appear to be intramuscular injections.

An interesting tidbit I haven't seen being mentioned - there's a polio oral vaccine, and an injection, but while the oral drops are much cheaper (and have lesser side effects), there's also a small chance of actually passing the virus.

Possibly dumb question: what's the risk for a European adult that has done all his vaccines since childhood?

A few months back my wife told me something about polio that I never knew... Polio emerged as an epidemic after the introduction of sanitation. The reason is that polio doesn't have such a terrible effect on infants, so the entire population has been exposed to it as babies and had developed immunity. So while sanitation reduced a lot of other horrible diseases that come from contaminated water, it prevented the population from getting this natural immunity in childhood, leading to an epidemic. And the people who suffered the worst during that time were the more affluent people who would have had better sanitation available to them. Because even though your neighborhood might be clean, you simply couldn't avoid coming in contact with polio in the great mixing bowl of a town or city.

What does "vaccine-derived" mean? What is the relation between the detected virus and the virus used in vaccines?

Interesting.

The tricky thing about finding it in London is that since they found it in sewage sampling, they don't yet know if it originated from the UK's vaccine program or an international source. They'll have to do more digging to narrow it down.

EDIT: as per peer comment from the UKHSA, it's believed to be from an international traveler or resident from a country where polio is still endemic and not yet eradicated. This is a good reminder to keep up on one's vaccinations, as herd immunity statistics are impacted by ubiquitous international travel.

> It is important that all countries, in particular those with a high volume of travel and contact with polio-affected countries and areas, strengthen surveillance in order to rapidly detect any new virus importation and to facilitate a rapid response.

If the virus is vaccine derived, shouldn't they search for the vaccine which is causing it ?

If I’ve had the vaccine as a child and possibly a booster around 15 years ago should I get a booster now?

I think we should move to mRNA technology for most of our vaccines.