A viewer asks about a recent scientific article showing experimental evidence 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. Is that a significant negative consequence that is occurring or will occur with the vaccination program underway against SARS-CoV-2?

Such things will happen and are almost inevitable in the case of viral infections, but this is not a reason to avoid vaccination, it is only interesting biological phenomenology that shows the perversity of the dilemma one faces when there is a microbial foe to contend with that becomes an intruder causing mayhem and disrupts people’s lives and constrains their doings. The fact there is a complication in using vaccination as a strategy to reduce susceptibility to illness and its severity does not justify throwing the baby out with the bathwater. So, in a sense, this is simply a further illustration of why it is best to stay with the herd and do what the herd does. In other words, if vaccination is made available, the ideal is for all to be vaccinated so people are on a par with one another, and if a more severe pathogen emerges under such circumstances it won’t hit the unvaccinated as a worse form of illness but will be attenuated to some extent if they have been vaccinated because there will be some benefit conferred in reducing disease severity even by a worse pathogen. The problem being highlighted in the research cited is that it is the unvaccinated who will suffer, so it is the price they pay for opting out of the vaccination program. But there is no reason for those desiring vaccination to reduce their liability on the theoretical possibility they are contributing as a participant in generation of a more pathogenic strain that will cause greater harm to the unvaccinated, and so should put themselves at greater risk by not taking advantage of the vaccine to begin with to save themselves from morbidity and potential mortality. Even with the theoretical downside this phenomenon represents, it indeed is the lesser of evils compared to having all be unprotected to begin with. There are still such strains created even when vaccination is not being conducted, so vaccination is not the only way in which amplification of a disease can come about, so we do not see this as justification for changing vaccine policy.