# The Ping Pong Vaccination Programming Challenge

Explore what it means to do computer simulation with respect to healthcare by writing a simple program that simulates the effect of virus spread. Modify it to see how changing assumptions changes the predictions

OR

try a fun if chaotic unplugged version that involves tossing plastic balls around a room full of people.

Vaccination programmes work best when the majority of the population are vaccinated. One way scientists simulate the effects of disease and vaccination programmes is by using computer simulations. But what is a computer simulation?

## Unplugged Simulation of Virus Spread

You can visualise what a simulation is with ping pong balls (or large plastic ball pool balls) bouncing around a crowd. Imagine having a large room full of people. A virus is represented by a ping pong ball, bouncing from person to person, infecting each person it touches. Each person who is hit by a ping pong ball and not already infected becomes infected. That means they toss that ping pong ball back into the crowd to infect more people, but they also toss an extra one too (and then they sit down: dead). Start with a few ping pong balls. Quickly the virus spreads everywhere and lots of people sit down (die).

You have run a physical simulation of how a virus spreads!

Now start again but ‘vaccinate’ 80 per cent of the people first: give them a baseball cap to wear to show who is who. If those people get a ping pong ball, they just destroy it: they infect no one else. Start with the same number of ping pong balls. This time, the virus quickly dies out and only a few people sit down (die). Not only are the vaccinated people protected but they protect many of the un-protected people too who might have died.

In these versions you are assuming each person is potentially coming into contact with anyone in the room as indicated by the balls being tossed around. If you assume people are only coming in to contact with their immediate neighbours (eg the 8 people closest to them) virus spread will be slower. Try an experiment where each infected person randomly passes a ball to half the people round them rather than tossing it. How does that change things?

What other variations can you think up to explore and so virtual experiments you can come up with?