over 7 billion human population, a 90% effectiveness is what? alright? please enlighten me. does anyone know what was the effectiveness of the smallpox vaccine that we did actually manage to eradicate successfully?
People infected by SARS-Cov2 seem to infect two to six other people [0]. Reduce this number by 90% and we are well below one infection per infected, so it is not sustained. This assumes that everyone would be vaccinated.
Currently we are doing something similar: each measure like wearing a mask, social distancing, meeting fewer people, ventilating rooms, finding infected people before they can infect someone else ("contact tracing") contributes to reducing the number of follow-up infections a bit. (This is why "but masks do not really work" is an ill-informed argument. They do not have to because they are meant to be used together with other measures to achieve reduction in spread)
A vaccine will protect us passively instead of requiring us to actively following these measures and will therefore be a lot more convenient.
In case of need, the Swiss cheese model:
https://mobile.twitter.com/sketchplanator/status/13127289416...
for SARS-COV-2 you need around 70% immunity in the population to achieve herd immunity
This is the required immunity of the population, but not the effectiveness of the vaccine. Inside the population there are groups that you cannot put the vaccine (smallest babies, immunosuppressed people, etc).
From:
https://www.cdc.gov/vaccines/vpd/mmr/public/index.html#:~:te....
The business-as-usual replication rate of covid appears to be somewhere around 4-6, meaning that if we have universal vaccination with something like 80% efficacy, the number of active cases will exponentially decay with no other measures taken (social distancing, masks, lockdowns, quarantines etc).
Covid is apparently around 3, and if you can vaccinate 90% of the population then an effectiveness of 75% would be the minimum you could get away with.
Probably 20% of people are responsible for 80% of infections. (People who work in shops or public places, people in large extended families, people who socialize a lot).
If you can identify and vaccinate those people it will be much more that 20% effective. (It might be hard to identify those but it's probably easy to identify people at low risk of spreading it and infer)
Keep in mind, that controlling covid is a giant win. We don't need to eradicate it, just get things under control.
Based on what we've seen there is no grey area. Either you fully control it which then ends up basically eradicating it e.g. Australia/NZ or you don't and then you end up like EU/US and going in and out of infection waves.
Right now if every activity would be fully available (concerts, conferences, airlines, etc.) every healthcare system across the world would probably be overwhelmed within 2 months, max.
Once we reduce the rates to a trickle, things are probably good enough.
I'm not saying that we shouldn't try to eradicate it, but as with everything, unfortunately, things are frequently taken to a point where they're "good enough" and no further.
The point of a vaccine is that you can't scale it back for populist appeasement; once you have broad immunity you keep broad immunity for long enough that you end up eradicating the virus almost involuntarily. In comparison, a lockdown is much more vulnerable to feel-good measures reducing the effectiveness.
Anything that reduces the R rate sufficiently will mean fewer outbreaks and reduce the strain on the hospital system.