A recent thread mentioned the use of weakened viruses in vaccines. It is also common wisdom that this is done. The intent more or less is that the body will react to the weakened viruses and produce antibodies, but the viruses themselves are too weak to create a viable infection.
In what way are viruses “weakened”? Is there an analogy in the animal or plant kingdom? For example, are “weakened” viruses actually viruses that have been starved of food and are too emaciated to move much? Viruses with structural damage/physical disabilities? Viruses with anti-survival behavioral disorders?
A live virus is “attenuated” by using a different virus instead. Ebola is too dangerous? Use Fbola or Gbola instead
AFAIK, the method used is to select the live virus from a population that is living in a non-human host, that is adapted/mutated to living in the non-human host, and has mutated to a form that is less virulent and less contagious in humans.
You don’t just find an attenuated virus lying around, you have to actively look for it and encourage it. And the dangers of an attenuated virus are (1) it may mutate back into something dangerous, or (2) it may be more dangerous (to some people) than you thought. But the biggest problem is that people and doctors just don’t like injecting/ingesting evil things like a “live attenuated polio virus”.
“Inactivated” viruses are inactivated by breaking them up into smaller pieces. The danger with an “inactivated” virus is that you may not have broken it up correctly.
Which suggests that the perfect vaccine would be an inactivated attenuated virus. The problem with that is that by the time you developed a safe inactivated attenuated virus, everybody would be dead, and the epidemic would be over.
yeah it is raised in a nonhuman host and allowed to mutate where it will no longer cause disease in humans but still trigger a human immune response. if nature allowed it to mutate to get to that state it will also eventually mutate into something else.
There are a couple of different concepts being mixed together here.
When people talk about “weakened” live-virus vaccines, they’re generally referring to viruses that have been passaged several times through a different host, like chicken eggs. This forces the virus to pick up mutations as it adapts to the new host. The idea is that eventually, you’ll end up with a virus that looks very close to the original virus - close enough to elicit a protective immune response - but that can no longer infect humans and cause disease. The danger of these mutations reverting and the virus returning to its original form is essentially nil, because the attenuated virus can’t replicate or spread efficiently. It would require several generations of reproduction to even have a chance of reverting.
There’s been talk about doing the same thing genetically - using molecular techniques to remove or mutate specific viral genes required to make people sick. I don’t know if there are any vaccines currently being used made with this technique.
Then there’s the idea of using a closely related virus as the vaccine. This was the original idea that lead to the whole concept of vaccination: Edward Jenner noticed that milkmaids were protected from smallpox by exposure to cowpox (vaca = cow in Latin, hence vaccination). Later, the variola virus, which is also closely related to smallpox, was used as a vaccine.
Next is the dead virus, where you just “kill” the virus and inject dead virus as the vaccine.
And now there’s the idea of using subunits, injecting just a single protein from the virus.
And so on. The Wikipedia page on vaccines has a nice list of the various different types.
