Here's a tweetorial on herd immunity, and why it's pretty cool #VaccinesWork medium.com/@gidmk/herd-im…

Herd immunity has nothing to do with cows! Saying "people aren't cows" is just displaying your ignorance for all to see

At its most basic level, it is simply maths

Mathematically, this means x/n = AR where x is the number of infected people and n is the total population

As I said, a simple metric of how infectious a disease is in practice

The higher the number, the more infectious the disease

What happens if people are immune?

The EFFECTIVE reproduction rate (R) is calculated based on the R0

Mathematically, it is: R0*y = R

Where y is the proportion of the population susceptible to the disease

Herd immunity means that each person passes on the disease to fewer than 1 person (on average), so the disease eventually peters out

I.e. the effective reproduction rate in the population is less than 1

R0*(1-HI) = 1

Where R = 1 and R0 is calculated based on the disease

Turning this around, we get:

HI =1-(1/RO)

Pretty cool, huh?

HI = 1-(1/4) to 1-(1/7) = .75-.86 = 75-86%

Measles can live for hours, even days, outside the body, and has an R0 of >12, which means that we need to vaccinate 95% of the population to be sure it won't spread

Australia has now eliminated endemic measles and rubella, and almost entirely eliminated many other infectious diseases, with some of the highest vaccination rates in the world #VaccinesWork

They will not only stop YOU from getting sick, they'll also stop you from passing diseases onto more vulnerable people like babies and immunocompromised people #VaccinesWork

Herd immunity is simple maths, nothing more, nothing less