Curious about how herd immunity works? Want to know how far we are from getting there? My latest #coronavirus story in the @washingtonpost is for you.

'A vaccine, or millions of deaths: How America can build herd immunity to the coronavirus' https://wapo.st/herd-immunity 

During an epidemic, being around a lot of people can be dangerous. But if those people are immune, instead of being a danger, they're more like a shield. This is the essence of what epidemiologists call "herd immunity."

https://wapo.st/herd-immunity 

A spreading disease will slow and eventually stop once a percentage of the population becomes immune. That percentage is called the “herd immunity threshold.”

We can use simulations to illustrate the herd immunity threshold in action.

https://wapo.st/herd-immunity 

Watch again. In the 40% community in the middle, the disease infects many healthy people. Only once the share of immune people crosses the 80% threshold are most of the healthy people insulated from the sick people.

https://wapo.st/herd-immunity 

Scientists are still trying to figure out the herd immunity threshold for SARS-CoV-2, the #coronavirus that causes covid-19. It's probably between 40% and 80%. The CDC has collected blood test data, and nowhere is the population close to herd immunity.

https://wapo.st/herd-immunity 

If you noticed those survey results are kind of old, good eye. We don't have more recent blood test data, but scientists from Harvard and Yale built a model that estimates #coronavirus seroprevalence in each state.

Still, nowhere even close.

https://wapo.st/herd-immunity 

There's another way to estimate how far we are from herd immunity. You take population size, herd immunity threshold, & fatality rate, multiply them together, and you get how many people would need to die before we get to herd immunity.

I made a grim calculator for the purpose.

Few leaders would welcome that much more death to build herd immunity. And so the world turns its hopeful eyes to a vaccine.

Read the story, which lets you reset the simulations, dig into the data, and tweak the assumptions, here: https://wapo.st/herd-immunity 

The article has made the homepage of The Post. Please give it a read. https://wapo.st/herd-immunity