Polio cases in Africa linked to new oral vaccine

"A problem" is a bit of an understatement... at this point it's basically caused the global polio eradication effort to fail. Wild type 2 poliovirus no longer exists anywhere in the world, and all infections with it over the last couple of decades are vaccine-derived. The original plan was that everywhere would switch to a bivalent oral vaccine without the type 2 virus, any remaining vaccine-derived outbreaks could be mopped up with monovalent vaccine, and then it would finally be eradicated for real. This failed - there were widespread outbreaks and targetted vaccination just caused the number of outbreaks to increase. The new oral vaccine was the fallback plan and the fact that this is already happening with it is not a great sign.

Title could start with the word Fewer it seems.

Thank you

Almost makes it sound like we would have eradicated polio had we not revived with with oral vaccines.

I don't think it's easy to summarize in a useful manner because it basically comes down to how a specific vaccine works.

For example, subunit vaccines like the whooping cough vaccine use a portion/fragment of the infectious agent, which means it is literally impossible for such a vaccine to cause the illness it is supposed to work on since there is none of that agent in the vaccine in the first place.

Attenuated vaccines, such as some polio vaccines and the MMR vaccine, include a weakened version of the infectious agent. These types of vaccines can result in a full-blown infection, especially in immunocompromised people.

So in short, the risk of a full-blown infection from a vaccine is going to depend on the type of vaccine, and I suspect there's variation within each type as well.

There's more info on the various types of vaccines at https://www.hhs.gov/immunization/basics/types/index.html

It depends on the vaccine.

My recollection:

There are two types of polio vaccine, one made from live germs and one made from killed germs. You cannot get polio from the killed polio version.

IIRC, polio vaccines are the primary cause of polio today.

This is pretty common, actually.

https://www.verywellhealth.com/what-is-a-live-virus-vaccine-... is a recent article with a partial list of common vaccines that are live. They tend to be more effective than alternative vaccines. And, unless you are immunocompromised, they are very unlikely to make you sick.

What makes the polio vaccine more complicated is that it is given orally, multiplies, passes through your body, and comes out in your feces. Which gives it a route by which it can infect people other than the person who received the vaccine. The same does not happen with injected live vaccines.

There is an inactivated polio vaccine that is given with a needle. That is used by the USA and most advanced countries. But it is more expensive, is harder to deliver (you need multiple shots on a schedule), and is less effective. It does protect the recipient against becoming paralyzed, but does not stop you from getting a mild stomach infection and passing it on in your feces where you can spread it to others. Therefore only the oral vaccination can halt an active community outbreak.

However the fact that the oral vaccine can also START a community outbreak means that we have to be careful where we use it.

Depending on how the vaccine works this is normal because the mechanism is infecting you with a low dose or weakened version of the virus, in simple terms.

>If a layman said this I would have dismissed them as a conspiracy nut

Should make you think about how most of us approach the problem, right? How often are we told a truth and despite not knowing anything about the topic we dismiss it as nonsense? If you're an expert in some niche field you'll know it happens all the time.

This is more or less why antivaxxers have at least some rational ground to stand on.

And this isn't the first time a Polio vaccine has caused the disease [0]:

  > In April 1955 more than 200,000 children in five Western and
  > mid-Western USA states received a polio vaccine in which the
  > process of inactivating the live virus proved to be defective.
  > Within days there were reports of paralysis and within a month
  > the first mass vaccination programme against polio had to be
  > abandoned. Subsequent investigations revealed that the vaccine,
  > manufactured by the California-based family firm of Cutter
  > Laboratories, had caused 40,000 cases of polio, leaving 200
  > children with varying degrees of paralysis and killing 10.

[0] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1383764/

Some vaccines are live attenuated virus.

You have to activate the immune system somehow. Sometimes presenting deactivated viruses or parts of viruses - viral capsids or nucleic acids - is not enough. Sometimes you can't find a good adjuvant.

You're only going to see this in the case of live attenuated vaccines. They can mutate and become virulent (since they were mutated to attenuate them in the first place).

You're not going to see that with mRNA vaccines, you're not going to see that with the adenovirus-vectored vaccines. You're not going to see that with inactivated virus vaccines (like most influenza[*] or CoronaVac or the Sinopharm COVID vaccines).

Live attenuated virus vaccines are one of the oldest vaccine methods and have been around since the 19th century. They're created by culturing the virus serially in artificial media and isolating a strain which is less virulent. Very brute force laboratory methods that only require the ability to culture the virus and an animal model of virulence with decent correspondence to human virulence.

One thing to remember is that we're dealing with a medical triage situation and its better to cause a very small amount of disease in order to eradicate most of it. People get hung up on the fact that medical science is a human activity that doesn't have perfectly flawless outcomes like in Star Trek, while the natural diseases are orders of magnitude worse.

[*] Except the Flumist nasal spray is live attenuated. Still with influenza that isn't likely a big deal. I would be willing to wager a bit that this technique is still being used there because the influenza virus is very good at getting past the nasal mucosa and we don't know how to engineer particles that do that very well (still no nasal COVID vaccine).

It depends on the vaccine. Some vaccines use a "weakened" form of the pathogen to trigger immunity response without causing actual disease, but sometimes, especially in cases of weaker immune systems, this can cause actual disease. This is not the case with most modern vaccines as they use different methods (and certainly not of covid19 vaccines), and certainly not what antivaxxers usually talk about (if anything, covid19-antivaxxers for example were proponents of getting _real_ infection instead of vaccine).

I am from Pakistan, one of the last remaining countries where Polio is not eradicated, all cases of Polio in Pakistan are from vaccines.

> This chart [2] (if accurate) is pretty eye opening.

It might be important to note that that chart specifically tracks deaths, not incidence.

At least according to the US CDC [0], paralytic polio (which I think most people think of when they see the word "polio") is generally the type that kills, usually due to paralysis of respiratory muscles and related symptoms.

Given all that, it turns out that the first iron lung that saw widespread use was developed in... 1928! (And other versions had been developed before that) [1] And iron lungs are fantastic for preventing death due to paralysis of respiratory muscles, as the lung does the muscles' job. This could either be until the patient recovers or permanent.

So in short, it's entirely possible the death rate fell because new tech allowed doctors to get better at keeping patients alive, rather than reducing the incidence, as the vaccines were generally intended to do.

> I've also read that the primary contributing factor to the decline (and recent rise) in polio is sanitary conditions.

At least according to the CDC, it's a mixed bag:

> In the immediate prevaccine era, during the first half of the 20th century, improved sanitation resulted in less frequent exposure and increased the age of primary infection, resulting in large epidemics with high numbers of deaths.

Can't really say much on the other claims or the paper, since that'd take way more expertise and/or time than I currently have.

[0]: https://www.cdc.gov/vaccines/pubs/pinkbook/polio.html

[1]: https://en.m.wikipedia.org/wiki/Iron_lung