Your immune system is a marvellous thing.  It keeps you safe from all sorts of infections and diseases, but sometimes it needs a bit of help from vaccines which “teach” the immune system how to respond if it were to come into contact with a disease for real.

In the current situation with Covid-19, the government is working hard to vaccinate the adult population to prevent the spread of the disease within the country.  If the uptake of the vaccine is large enough, then the hope is that people who have not had the vaccine will be protected too because there is nowhere for the virus to spread. This is a form of herd immunity, but what exactly is that?   Despite how it sounds, it isn’t actually anything do do with cows or sheep!

Herd immunity comes from having enough people being immune to the disease that they are not able to catch it and therefore pass it onto people who are not immune.  If you have a Jenga set, (or similar), and some stickers you can demonstrate how this works:

  1. Place stickers on the ends of 10 random blocks then stack all the blocks to build a tower.
  2. The tower of blocks represents a group of people like the community you live in. You will act as an infectious disease, spreading through the community and infecting people. The stickered blocks are people who have been vaccinated against the disease and are protected from infection.
  3. ‘Infect’ the community by, one by one, removing the blocks with no stickers. Each block that is removed is a person that has become infected. The stickered blocks (vaccinated people) cannot be removed. What happens to your tower? Why?
  4. What happens if you ‘vaccinate’ more people in the community? Place stickers on 35 more blocks so that most of the blocks now represent vaccinated people. Build another tower with your blocks. Again, ‘infect’ people by removing blocks with no stickers from the tower. What happens to your tower? Why?

The first tower fell down quickly because not enough blocks were protected by vaccination, so too many were infected and removed. The second tower should stay standing, because when most people in a community are protected by vaccination, it makes it difficult for the disease to spread. This is called herd immunity. Herd immunity is crucial to protect those who are unable to receive vaccines, including people who
have a health condition that impairs the function of their immune system, which is why the government have made targeted the vaccination programme for Covid-19 at priority groups, (those who are most likely to become really ill if they catch it), first.

I hope this helps you to understand why it is important for the uptake of the Covid-19 vaccinations to be as high as possible.

If you would like to take part in tomorrow’s activity, you will need an old, transparent cd, the cardboard tube out of a kitchen roll and some black card or paper.

Until next time, Keep calm and apply some Science!

This activity has been taken from the downloadable resources at