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What's interesting is that the same principle doesn't seem to apply for viral infections. The smallpox vaccine is just as effective today as it was a couple de

What's interesting is that the same principle doesn't seem to apply for viral infections. The smallpox vaccine is just as effective today as it was a couple decades ago. Then again the flu is constantly mutating so maybe it's just contingent on the type of disease.

not2b 5y ago
Depends on which virus. Flu shots have to be changed every year, but measles shots appear to give lifetime immunity.
- roywiggins 5y ago
  Flu doesn't evolve to resist each vaccine, it's just a different strain becoming prevalent each year. I'm not sure what the mechanism behind that is, but it was happening before the flu vaccine existed.
  - bink 5y ago
    Is there much difference conceptually between a virus mutating in a body and then finding ready hosts amongst the vaccinated if there is a large vaccinated population and a bacteria that has a resistance to an antibiotic spreading in a host that is receiving that antibiotic? Sorry for probably not using the right terminology here but they seem closely related to me.
    - exyi 5y ago
      Antibiotic resistance is usually on plazmids which can be exchanged between different bacteria (often even between different bacterial species). So only one bacteria needs to find the right gene and it starts spreading. Viruses have really small genomes and simply adding a gene for bypassing immunity does not work. It would need to restructure it's surface proteins so that the immune cells can't recognize it anymore, but this restructure often breaks the virus. Also there is the thing that antibiotics are present at low concentrations everywhere which makes small but constant pressure for the resistance genes. > On a larger scale, since 1940, antibiotics have become an omnipresent pollutant in environments of all types (55). Even in places largely untouched by humans, we can find antibiotic compounds and, with them, ARGs (56–59). In recent years, we have learned that even low levels of antibiotic pollution select for high levels of resistance (60–62). Additionally, regardless of the biome or their ability to clear pollutants, humanity’s worldwide industrial-level use of antibiotics has resulted in a steady stream of antibiotics into the environment, without ever allowing natural systems to return to baseline levels (63). Immunity does not come in this constant small pressure. You either have it and then the virus is dead quickly, so it does not have much time for finding mutations. Or you don't have it, so there is no pressure for the mutations.
  - exyi 5y ago
    Definitely, there is selection pressure for new strains so that it can reinfect people which have immunity from last year. The flu virus is really good in mutating because its genome is made 7 or 8 parts which can be exchanged between strains. Most other viruses don't have these segmented genomes and are somehow stuck in a local optimum, so they can't evade the immunity so easily.
    - deleted 5y ago
      [deleted]

not2b 5y ago

Depends on which virus. Flu shots have to be changed every year, but measles shots appear to give lifetime immunity.

roywiggins 5y ago
Flu doesn't evolve to resist each vaccine, it's just a different strain becoming prevalent each year. I'm not sure what the mechanism behind that is, but it was happening before the flu vaccine existed.
- bink 5y ago
  Is there much difference conceptually between a virus mutating in a body and then finding ready hosts amongst the vaccinated if there is a large vaccinated population and a bacteria that has a resistance to an antibiotic spreading in a host that is receiving that antibiotic? Sorry for probably not using the right terminology here but they seem closely related to me.
  - exyi 5y ago
    Antibiotic resistance is usually on plazmids which can be exchanged between different bacteria (often even between different bacterial species). So only one bacteria needs to find the right gene and it starts spreading. Viruses have really small genomes and simply adding a gene for bypassing immunity does not work. It would need to restructure it's surface proteins so that the immune cells can't recognize it anymore, but this restructure often breaks the virus. Also there is the thing that antibiotics are present at low concentrations everywhere which makes small but constant pressure for the resistance genes. > On a larger scale, since 1940, antibiotics have become an omnipresent pollutant in environments of all types (55). Even in places largely untouched by humans, we can find antibiotic compounds and, with them, ARGs (56–59). In recent years, we have learned that even low levels of antibiotic pollution select for high levels of resistance (60–62). Additionally, regardless of the biome or their ability to clear pollutants, humanity’s worldwide industrial-level use of antibiotics has resulted in a steady stream of antibiotics into the environment, without ever allowing natural systems to return to baseline levels (63). Immunity does not come in this constant small pressure. You either have it and then the virus is dead quickly, so it does not have much time for finding mutations. Or you don't have it, so there is no pressure for the mutations.
- exyi 5y ago
  Definitely, there is selection pressure for new strains so that it can reinfect people which have immunity from last year. The flu virus is really good in mutating because its genome is made 7 or 8 parts which can be exchanged between strains. Most other viruses don't have these segmented genomes and are somehow stuck in a local optimum, so they can't evade the immunity so easily.
  - deleted 5y ago
    [deleted]