Polio cases in Africa linked to new oral vaccine

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/

Right, I believe the messaging around vaccines exacerbates the issue too. Especially with mrna covid-19 vaccines, the condescending tone used by the CDC and media outlets while implying no safety risks throw people off. If you don't upfront say there's some risk and explain it it gives room for antivaxxer propaganda that builds on those doubts. IMHO, the media campaigns for the mRNA vaccines did the opposite of that.

All existing vaccines have risk, however they're at least a factor off 100 safer. I find if you explain this, and why they're still a good choice people respond well. Especially if you give the history of people / scientists working on them. There was a study posted on HN a while back that showed mothers who were given an explanation months before birth had a higher vaccination uptake rate.

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).