Covid-19 Cepiva

Uporabnik R0KY je napisal:

Po raziskavah virus bolj mutira v necepljenih.

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Vaccines Are Pushing Pathogens to Evolve | Quanta Magazine

Just as antibiotics have bred resistance in bacteria, vaccines can potentially lose their effectiveness over diseases they controlled. Researchers are working to head off the evolution of new threats.

www.quantamagazine.org

Read and his colleagues vaccinated 100 chickens, leaving 100 others unvaccinated. They then infected all the birds with strains of Marek’s that varied in how virulent — as in how dangerous and infectious — they were. The team found that, over the course of their lives, the unvaccinated birds shed far more of the least virulent strains into the environment, whereas the vaccinated birds shed far more of the most virulent strains. The findings suggest that the Marek’s vaccine encourages more dangerous viruses to proliferate. This increased virulence might then give the viruses the means to overcome birds’ vaccine-primed immune responses and sicken vaccinated flocks.

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Imperfect Vaccination Can Enhance the Transmission of Highly Virulent Pathogens

A study using Marek's disease virus in poultry shows that by reducing natural selection against highly virulent strains, imperfect vaccination enables the spread of viral strains that would otherwise be too lethal to persist.

journals.plos.org

Uporabnik MrDaco je napisal:

Koliko jih je v bolnici in koliko umrlih... samo to še lahko šteje.

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Uporabnik R0KY je napisal:

Zato iz vseh visokoprecepljenih drzav prihajajo novi straini ane?

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Evolutionary biologists aren’t surprised that this is happening. A vaccine is a novel selection pressure placed on a pathogen, and if the vaccine does not eradicate its target completely, then the remaining pathogens with the greatest fitness — those able to survive, somehow, in an immunized world — will become more common. “If you don’t have these pathogens evolving in response to vaccines,” said Paul Ewald, an evolutionary biologist at the University of Louisville, “then we really don’t understand natural selection.”

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Perhaps vaccination was inciting evolution, causing strains of the bacteria that lacked the targeted proteins, or had different versions of them, to survive preferentially.

Studies have since backed up this idea. In a 2014 paper published in Emerging Infectious Diseases, researchers in Australia, led by the medical microbiologist Ruiting Lan at the University of New South Wales, collected and sequenced B. pertussis samples from 320 patients between 2008 and 2012. The percentage of bacteria that did not express pertactin, a protein targeted by the acellular vaccine, leapt from 5 percent in 2008 to 78 percent in 2012, which suggests that selection pressure from the vaccine was enabling pertactin-free strains to become more common. In the U.S., nearly all circulating viruses lack pertactin, according to a 2017 CDC paper. “I think pretty much everyone agrees pertussis strain variation is shaped by vaccination,” Lan said.

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