It's not even necessarily needing in the way you imply. Evolution is based on completely random mutations that happen at random times and amounts. If there's only a certain new type of food that's available, either a random mutation happens to come along that randomly allows the organisms to eat this new stuff, or they all die out and go extinct. There's no set progression or driver of evolution, though there can be pressures that cause organisms with certain mutations to live or die more frequently. If the organism can live and reproduce more with a certain random mutation in its genome, then those organisms continue to breed and the mutation takes over in the population.
This means that the fewer people who are infected with covid, be they vaxxed or not, the less chance for these random mutations there is, and less of a chance for more or different variants. And if infections are running rampant in more people, there's more replication of the virus overall, therefore more chances for a random mutation in the replication process to occur. More random mutations, more of a chance for something bad to happen with a variant. And while it's generally true that viruses mutate in order to spread the most, which includes keeping the host alive enough to keep replicating and spreading the virus, there's no guarantee that a random mutation won't come along that causes other weird symptoms, or can create more long term health problems. Because even if the host survives and spreads the virus, it doesn't care if the host is ok or negatively affected in the process, as long as he virus can continue to replicate and spread.
Sorry for the long-winded response, but I thought I'd share some insight.
It's not even necessarily needing in the way you imply. Evolution is based on completely random mutations that happen at random times and amounts. If there's only a certain new type of food that's available, either a random mutation happens to come along that randomly allows the organisms to eat this new stuff, or they all die out and go extinct. There's no set progression or driver of evolution, though there can be pressures that cause organisms with certain mutations to live or die more frequently. If the organism can live and reproduce more with a certain random mutation in its genome, then those organisms continue to breed and the mutation takes over in the population.
This means that the fewer people who are infected with covid, be they vaxxed or not, the less chance for these random mutations there is, and less of a chance for more or different variants. And if infections are running rampant in more people, there's more replication of the virus overall, therefore more chances for a random mutation in the replication process to occur. More random mutations, more of a chance for something bad to happen with a variant. And while it's generally true that viruses mutate in order to spread the most, which includes keeping the host alive enough to keep replicating and spreading the virus, there's no guarantee that a random mutation won't come along that causes other weird symptoms, or can create more long term health problems. Because even if the host survives and spreads the virus, it doesn't care if the host is ok or negatively affected in the process, as long as he virus can continue to replicate and spread.
Sorry for the long-winded response, but I thought I'd share some insight.
Exactly, the direction of evolution is determined by the environment.