BRET WEINSTEIN (GUEST): Not only is there the question of the harms that they may do to individuals who get them, but there's also a question about what they will do to the epidemic itself. So there are there's a category we desire when we make a vaccine that would be what we call perfect, which means that there are no breakthrough cases in this case. In this case we don't have perfect vaccines. And although the numbers are very good, they do indeed prevent most people from contracting COVID, enough people who have the vaccines come down with what we call a breakthrough case, so that they exert a kind of selection on the virus, and that selection can cause the epidemic to change by creating escaped mutants or variants.
TUCKER CARLSON (HOST): So the vaccine itself could make the coronavirus into something different and potentially more harmful.
WEINSTEIN: Yes, people will remember from the beginning of the pandemic when there was a lot of talk about something called herd immunity, herd immunity arises when enough people have immunity to the virus, that an infected person's pathogen can't find a next victim and if the number of next victims drops low enough, then the pathogen will go to extinction. The problem is that the vaccines, being imperfect causes selection on the virus for those variants that are invisible to the immune system.