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Confusion over various endpoints for the covid pandemic is flaring up again. Eradication, elimination, containment, suppression, transition to seasonal/endemic covid, etc. are terms that even scientists use in inconsistent ways.
Here's a decent explainer (though, unhelpfully, some scientists and policymakers may use the terms used here in ways that are distinct from how they're used here): https://theconversation.com/eradication-elimination-suppression-lets-understand-what-they-mean-before-debating-australias-course-142495
Eliminating covid, eradicating it from the face of the earth except for samples kept in (ideally highly secured) labs, as we have done for smallpox, is *extremely* unlikely.
Smallpox & covid could hardly be more different from an eradication-feasibility standpoint. Smallpox isn't transmissible from animals or insects to humans, so there's no "reservoir" where it can thrive even when humans have herd immunity. Not so for covid.
Smallpox is also super-visible during the infectious phase so it was easy to find cases and quickly isolate/vaccinate everyone in proximity. Not so for covid.
There's confusion about what herd immunity does. It means that the pool of hosts (epidemiology's creepy term for people) is shrinking, eventually to the point that spread is slowed way down. In very rare cases that means eradication/elimination... but...
In most cases, herd immunity doesn't eliminate/eradicate a virus. It ends the pandemic phase, creating a more manageable situation, e.g. seasonal/endemic transmission (like flu) or containment (local/regional elimination in some places for some periods of time)
Herd immunity (which is generated by infection and/or vaccination) can also achieve suppression, stopping exponential spread, but with ongoing transmission at lower levels.
It's not a light switch, but there will be benchmarks along the way. Even at lower levels, immunization can start to make a difference in hospitalizations and deaths pretty quickly if we get prioritization right.
Gradually, it'll become easier to prevent exponential growth with fewer changes to our regular routines. But if we return to baseline levels of in-person interaction too quickly, then controlling exponential spread will require higher levels of vaccination.
New variants may be more transmissible (requiring higher levels of intervention to prevent exponential growth in cases), more virulent (counteracting the effects of low levels of vaccination on reductions in hospitalizations/deaths) or less responsive to current vaccines, but...
The effect of variants won't be a light switch either. At the individual level, risk to unvaxxed may be higher, risk to vaxxed may be a little higher, too. But at the population level, we're still likely to see big benefits from vax even w/ variants.
These factors interact w/ each other. Low levels of immunization will reduce deaths/hospitalizations faster if those of us who aren't fully vaxxed maintain other interventions (reduced in-person contact, masks). Faster spread to more people -> faster evolution of new variants.
