Exponential decay - the maths that explains the end phase of Covid-19

Exponential dynamics explains why it is important to maintain precautions such as wearing masks even as rising vaccination rates drive case numbers down

It could be months before the US has vaccinated enough people to put herd immunity within reach. PHOTO: AFP
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(NYTIMES) - The United States has vaccinated more than half of its adults against Covid-19, but it could be months until the country has vaccinated enough people to put herd immunity within reach (and much of the world is still desperately waiting for access to vaccines). Places with rising vaccination rates, like the US, can look forward to case numbers coming down a lot in the meantime. And sooner than you might think.

That's because cases decline via the principle of exponential decay.

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