Read et al.: "Imperfect Vaccination Can Enhance the Transmission of Highly Virulent Pathogens"; if a vaccine completely eliminated the virus (no transmission), that's perfect; it (COVID vax) DOES NOT!
by Paul Alexander
The results suggest that disease interventions e.g. leaky vaccines (e.g. COVID vax) that aim to prevent disease symptoms without preventing transmission can have dangerous evolutionary consequences
This work by Read et al. on chickens as it relates to Marek’s, has heavy bearing on what we are seeing with the COVID injections, especially as to the sub-optimal immune pressure on the antigen that is driving selection pressure for more infectious (and more virulent) sub-variants/clades. You read this research and take the nuggets that can help explain what we are seeing re COVID injections.
‘Could some vaccines drive the evolution of more virulent pathogens? Conventional wisdom is that natural selection will remove highly lethal pathogens if host death greatly reduces transmission.
Vaccines 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.’
There is a theoretical expectation that some types of vaccines could prompt the evolution of more virulent (“hotter”) pathogens. This idea follows from the notion that natural selection removes pathogen strains that are so “hot” that they kill their hosts and, therefore, themselves. Vaccines that let the hosts survive (e.g. reduce symptoms as in the case of the COVID vaccines) but do not prevent the spread of the pathogen (as in the case of COVID vaccines given the vaccinal antibodies are largely non-neutralizing and do not stop infection, replication, or transmission etc.) relax this selection, allowing the evolution of hotter pathogens to occur (as in the case of COVD vaccines). This type of vaccine is often called a leaky vaccine (as in the case of COVID vaccines). When vaccines prevent transmission, as is the case for nearly all vaccines used in humans, this type of evolution towards increased virulence is blocked (COVID vaccines work oppositely enhancing transmission).
But when vaccines leak, allowing at least some pathogen transmission, they could create the ecological conditions that would allow hot strains to emerge and persist.’
Not all vaccines prevent infection. Some, known as leaky vaccines, prolong host survival or reduce disease symptoms without preventing viral replication and transmission. Although leaky vaccines provide anti-disease benefits to vaccinated individuals, new research by CIDD’s Andrew Read, David Kennedy and colleagues at the Avian Oncogenic Virus Group in the United Kingdom, and The University of New England in Australia, has demonstrated that leaky vaccines can make the situation for unvaccinated individuals worse. Leaky vaccines work by enhancing host immunity to a particular pathogen, without necessarily blocking or slowing viral replication. The result is that infected but vaccinated individuals have extended survival, allowing highly virulent pathogen that would normally reach an evolutionary dead-end in a dead host, can transmit. The evolutionary consequences of high virulence are thus reduced and these pathogens can be selectively favored as a result of leaky vaccination.’