Herd immunity is a veterinary concept, which makes it hard to estimate in human populations since there's a metric ton of sociological and anthropological factors to consider in addition to epidemiological ones. As a rule of thumb, it can be estimated as (R0 - 1) / R0. That is to say, if the reproduction number was 2.4, then it's 58.33%. If the UK variant were indeed R=0.4 more contagious, that'd be 64.28%. Some other estimates had come up with a reproduction number as high as 5.7, which would mean the herd immunity threshold is 82.45%...
But like I said, that's a simplistic approximation. People are constantly being born or dying, move their homes, have distinct social circles with distinct degrees of social interaction, etc. which could make it not only higher or lower than the estimates above, but constantly changing with time.
On the other hand, the social aspect of the pandemic will likely end much earlier than the outbreaks themselves once at-risk groups that are only a minority of the population but make up more than 90% of Covid-19 deaths are vaccinated.
Now for the Brazilian news, Coronavac's results are out and they seem much better than I was expecting (78% overall, 100% for severe cases). EUA was just requested this morning for it, and the same is going to happen today for the AZ vaccine. These are especially relevant since we can produce both of these locally.
The Butantan Institute has some 10 million doses of imported Coronavac for immediate use and will begin producing up to one million doses a day, with an increase to double that number in April as soon as it is finished making this year's flu vaccines. The Fiocruz Foundation, which will produce the AZ vaccine, also has imported a few million doses, but I'm not sure how rapidly they can produce it.
Pending some unexpected delays, such as Bolsonaro deliberately tampering with the approval procedures, vaccination of at-risk groups will begin on the 20th of this month, for free, in the public healthcare system.
Last edited by haxxiy - on 08 January 2021