Rising vaccination rates mean #COVID19 case numbers will fall a lot even before reaching herd immunity. And sooner than you might think. That’s because cases decline via exponential decay.
My piece in the @nytimes @nytopinion explains. 1/6 https://www.nytimes.com/2021/04/29/opinion/covid-exponential-decay.html

Exponential growth means case numbers can double in just a few days. Exponential decay is its opposite. It means case numbers can halve in the same amount of time. 2/6

Understanding exponential dynamics makes it easier to know what to expect: Why things will improve quickly as vaccination rates rise and why it’s important to maintain some precautions after case numbers come down. 3/6

It is possible to bring case numbers down quickly via exponential decay even before reaching herd immunity. We just need to keep transmission rates below the tipping point between exponential growth and exponential decay. 4/6

The road to herd immunity won't be smooth. It’s natural for people to want to ease precautions when cases fall and be reluctant to step up precautions when cases rise. The tricky part is knowing how much to ease up while keeping cases trending down. 5/6

Every vaccination helps keep us in the realm of exponential decay. So does everything else we do to slow the spread of the virus, like masking and distancing.
The US is still a long way from herd immunity but things could improve a lot before then. And sooner than you think. 6/6