Infection with at least some of those "common cold" human coronaviruses seems to have much the same effects on kids and the elderly (and maybe everyone else too) as Covid-19. At least part of the reason we're not seeing a huge pandemic of those is that lots of people already have immunity, but that also makes infecting people with them less useful - the people who already have immunity to those aren't likely to develop new immunity, and the people who don't presumably won't necessarily develop immunity that crosses over to Covid-19.

(Unfortunately, since common cold research is a lot less big, glamourous and high-profile than Covid-19, I don't think we know a huge amount for sure about the other human coronaviruses - and what we do know isn't exactly front-page headline news.)

I read earlier in the year... early in the news about the outbreak, a skeptical view that suggested the reason for this 'epidemic' had something to do with the relatively new ability to apply fast genetic testing to a 'fairly common cold'

edit to remove the phrases: "pandemic" & "new normal"

Doctors can’t do that ethically, but people could spread it among themselves. It’s the chickenpox-party solution. I don’t think it’s practical though given how easy it is to confuse another Coronavirus for Covid symptoms.

Deploying a coronavirus to immunize against covid is a vaccine by definition and deciding to not call it a vaccine as a matter of syntax doesn't make the ADE risk go away

Call it a vaccine or not, common cold virus don't have to be developed because they already exist.

vaccines against COVID have already been developed. They already exist. Designing them took a couple of weeks. What takes time is testing them to make sure they are safe and effective. The cold causing coronaviruses would also have to be tested for safety and efficacy in an application of preventing COVID-19. That's what the bulk of "developing" a COVID vaccine means in our modern context - testing through clinical trials. The first RNA vaccine against COVID "existed" a week after SARS-COV-2 was sequenced, and vaccines that use parts of the virus itself "existed" basically immediately after SARS-COV-2 started existing. Using the cold virus is actually a harder problem scientifically since you're using a different strain of virus to protect against SARS-COV-2 epitopes - the mechanism and safety profile is harder to predict and evaluate.

Of course we don't yet know how effective it is. But how don't we know its safety profile? Why should a cold virus be more dangerous just because we use it as a vaccine, especially if we spread it the "usual" way as opposed to injecting it?