Alpha and Delta
The original Covid-19 has an R number of 3. The alpha (Kent) variant is 70% more infectious (R number = 5). The delta (India) variant is 30 to 100% more infectious than the alpha variant. So the R number is 8. This means that for people who are not immune, each person will infect about eight people, if no-one is taking precautions.
So it's not too surprising that in the last three days, the number oof new cases has been 4330, 5274, 6238. It's starting to look exponential. We've been here before.
With an R number of 8, you need 1 - 1/R = 88% of the population to be immune to have herd immunity. This probably means the we'll never get there.
Back when the R number was 3, we needed 66% to be immune, and that would likely to be reached with vaccination. Even when the R number was 5, it was maybe possible to reach the 80% needed for herd immunity. But 88%? I don't think so.
Why is 88% immunity not possible? Because there are simply too many people who are not willing to take a proven safe jab, and prefer the risk of getting the disease.
And why aren't they willing? Because to understand pandemics and how to deal with them, you need to understand maths, statistics, physics, chemistry, biochemistry, genetics and how to do research (hint, watching youtube videos isn't research). And most people don't have all these understandings. Many people don't have any of them. So all they can do, is find someone to trust who does know this stuff, and trust them.
In the UK, we're lucky; a lot of people trust the NHS. In America, and many other countries, there's nothing like the NHS, and they don't trust their own governments.
But far too many people trust Tilly on Twitter or Fred on Facebook, because Tilly has lots of people repeating what she says, and Fred has a loud voice and a confident demeanour.
And there's people like Andrew Wakefield, the struck-off doctor, telling people that vaccines are bad. There's people claiming that vaccines are untested, or that no-one knows what's in them, or that they include a microchip.
So the outlook is bad. We beat polio, because people knew how terrible the disease was, and everyone was keen to eradicate it. We beat smallpox. We beat mumps, rubella, pertussis.
So what changed? People are unwilling to believe people who know stuff, and think that Wally from Whatsapp is a better source of good advice.