For instance if Delta has an R0 of 8, and we're 100% vaccinated, and the vaccine has an efficacy of 85% against infection, the resultant Rt would be 1.2:
8 * (1 - (1 * 0.85))
So that means that some other form of mitigation on top of 100% vaccination would be necessary to stop the spread.
But for mutations with lower R0, or higher vaccine efficacy, herd immunity may still be possible.
https://covid.cdc.gov/covid-data-tracker/#variant-proportion...
https://www.businessinsider.com/delta-variant-made-herd-immu...
I think that's an overstatement of the links you are sharing.
Several parts of the country have pushed Rt < 1, so there are clearly things we can do to stop the spread, through a combination of vaccination and other mitigation measures.
And the definition of herd immunity is literally what protects people from infection. (Herd immunity includes vaccine immunity.) And even before the HIT, vaccination reduces contagion, reduces the doubling rate, buys time to implement further mitigation to drive down Rt < 1, and saves lives.
Anyway, what the Astra Zeneca guy is saying is just that our vaccines are not effective enough against infection to get Rt < 1 on their own.
mRNA Vaccines do have efficacy against infection, and additional effectiveness against infecting others; it's just that they're still not quite as effective as their effectiveness against hospitalization and death.
Improved vaccines, or the third-shots happening now (which do temporarily improve infection efficacy) improve those stats. Herd immunity isn't yet theoretically impossible even if it's a practical impossibility in our populations.
It probably is true that we can't go back to the way we were pre-covid, no distancing, no masks, and avoid COVID spread. We're not there and may never be since there's a likelihood that some variant of COVID will be endemic.
But there's plenty we can do - vaccination, and mitigation to get Rt < 1 during spikes. Those two practices protect people from infection.
Agreed that everyone able should get vaccinated.
The point is Rt. If Rt is above 1, and the disease has a degree of mortality similar to what it has now, then it means the case count will double at some rate. And ICUs will fill up, and people will start dying from things like broken legs and pneumonia from not being able to get sufficient care. Does that make sense? That's just what Rt > 1 means; case counts are doubling. If Rt is above 1, then if you don't want the disease to eat the world, something needs to happen to get Rt back below 1. If not, it will happen naturally, solely through natural immunity and unnecessary death.
So the goal simply needs to be to keep Rt below 1, or to knock it back below 1 before prevalance becomes dangerous and threatens ICUs.
But that doesn't necessarily mean lockdowns. If there's a spike but already a good level of immunity, it might just mean masks on public transportation for a couple of months, or people naturally choosing to go out to eat three fewer times a month, or whatever.
The measure of required mitigation depends entirely upon the circumstance in the moment. If Rt spikes a little, you don't need to do much. If it spikes a lot, you need to do more. But with enough vaccination, we might not ever need full lockdowns for covid again.
For herd immunity, you also need to take into account that infected people—even symptomatic ones—are less infectious to others, if they're vaccinated.
Last I heard, the CDC gave a 95% CI of the mRNA vaccines being 26% - 84% against infection (from Delta), and there's an additional 40% - 60% protection against infecting others (I've seen that estimate in multiple places but I don't know the source). If that's true, it suggests an overall range of 55.6 - 93.6 effectiveness against infecting others.
Absolutely, I'm just stressing it cause people have used the word 'efficacy' to measure lots of different things!
300 new cases / day, 5500 active cases, and 2 deaths / day, for a country with 10M people. (3 new cases / day, 55 active cases, 0.02 deaths / day, per 100,000.)
Compared with, say, the US: 112,000 new cases / day, 9,800,000 active cases, 2000 deaths / day. (34 new cases / day, 3000 active cases, 0.6 deaths / day, per 100,000.)
I'd say you're in better shape than we are.
I even saw different regions of my country do this. Fast forward 2 months and the situations are reversed and so is the finger pointing.
It’s absurd.
It's an unfortunate circumstance that 90% of people being fully vaccinated might not be enough to stop COVID-19 in its tracks. Even just 1% of people being unvaccinated makes millions of people who could catch, mutate, and transmit the virus. Especially if those people were loosely clustered together, and didn't take precautions against spreading disease, they could possibly keep the virus active (and hospitals busy) for a long time on their own.
I'm vaccinated, and in a country with 80% of people on two doses and 90% on one dose. But we still have a lot of cases, and a lot of people stuck on ventilators in hospitals.