Sound familiar? The only difference is that the chicken virus has a much higher mortality rate in unvaccinated chickens than does Covid in unvaccinated people, but nevertheless, the vaccine is keeping people alive that would otherwise die (or at least get sick enough to self-quarantine as opposed to going out into public, vaccinated, feeling invincible, and with little or minor symptoms).The deadliest strains of viruses often take care of themselves — they flare up and then die out. This is because they are so good at destroying cells and causing illness that they ultimately kill their host before they have time to spread.
But a chicken virus that represents one of the deadliest germs in history breaks from this conventional wisdom, thanks to an inadvertent effect from a vaccine. Chickens vaccinated against Marek’s disease rarely get sick. But the vaccine does not prevent them from spreading Marek’s to unvaccinated birds...
The reason this is a problem for Marek’s disease is because the vaccine is “leaky.” A leaky vaccine is one that keeps a microbe from doing serious harm to its host, but doesn’t stop the disease from replicating and spreading to another individual. On the other hand, a “perfect” vaccine is one that sets up lifelong immunity that never wanes and blocks both infection and transmission...
Moving on...
I won't get into the specifics of the experiments - you can read about them in the PBS article if you like or in the full text of the study, but the findings?“Previously, a hot strain was so nasty, it wiped itself out. Now, you keep its host alive with a vaccine, then it can transmit and spread in the world,” Read said. “So it’s got an evolutionary future, which it didn’t have before.”
But does this evolutionary future breed more dangerous viruses? This study argues yes...
https://www.pbs.org/newshour/science/tt ... -dangerousOne way to look at that experiment is that shows vaccinating birds kills unvaccinated birds. The vaccination of one group of birds leads to the transmission of a virus so hot that it kills the other birds
From the study itself:
https://journals.plos.org/plosbiology/a ... io.1002198Vaccines that keep hosts alive but still allow transmission could thus allow very virulent strains to circulate in a population. Here we show experimentally that immunization of chickens against Marek's disease virus enhances the fitness of more virulent strains, making it possible for hyperpathogenic strains to transmit. Immunity elicited by direct vaccination or by maternal vaccination prolongs host survival but does not prevent infection, viral replication or transmission, thus extending the infectious periods of strains otherwise too lethal to persist. Our data show that anti-disease vaccines that do not prevent transmission can create conditions that promote the emergence of pathogen strains that cause more severe disease in unvaccinated hosts.
And something I didn't even know:
Hear that? Leaky vaccines for avian flu are BANNED in Europe and the US. I never once heard this concern raised when the Covid vaccines were being developed.Like Marek’s vaccines, vaccines for avian influenza are leaky. For this reason, they’re banned from agricultural use in the U.S. and Europe
The authors do go on to hypothesize how imperfect vaccines affect humans:
Well, we have nearly a year's worth of data, and I think we already know the answers to some of those questions. It does NOT keep patients from getting infected or transmitting the virus. Also may explain why the Delta wave has been lingering for longer than the past waves before we had vaccines. This is playing out before our very eyes. People need to start recognizing that. Now to be fair, the authors do not necessarily suggest that leaky vaccines are bad. As they note, "even if this evolution happens, you don’t want to be an unvaccinated chicken." But they stress that we do "need to consider the evolutionary consequences...[of] leaky transmission."To test the imperfect vaccine hypothesis in humans, you would need monitor the vaccine response for either a large or isolated population for a long time. Doing this would allow a researcher to gauge how the vaccine interacts with the virus and if that relationship is evolving. Does the vaccine merely reduce symptoms, or does it also keep patients from getting infected and transmitting the virus?