2.2

R, how it works

# The reproductive number - R

Watch this video from the London School of Hygiene and Tropical Medicine, in which Professor Judith Glynn explains the reproductive number, R.

Make a note of the crucial concepts Prof Glynn introduces, such as:

1. R0: the number of new cases each case produces (on average)
2. Susceptibility: the proportion of the population who are capable of contracting the infection
3. Resistance: the proportion of the population who are not (either through vaccination or acquired immunity)
4. R: the (net) reproductive number which is a product of R0 x susceptibility
5. The Herd Immunity Threshold: the proportion of the population that need to be immune for R=1
6. Vaccine efficacy: the proportion of people in whom the vaccine works (i.e. they are immune)

Once you’ve made a note of these things, look at the video in the next step, which is an interview with Rhiannon Edge, a specialist in vaccination at Lancaster Medical School. Listen for the point where we discuss vaccine efficacy, as you’ll need to know this if you are going to take the test in the following step, in which you’ll be carrying out a calculation similar to the one Prof Glynn demonstrates for Ebola, but using flu instead.

Professor Glynn’s presentation is a step from the FutureLearn Ebola course, which was produced by the London School of Hygiene and Tropical Medicine. The Ebola epidemic of 2013-2015 is used as an example, but same framework applies to influenza and any other infectious disease.

You can watch the video at: https://www.futurelearn.com/courses/ebola-in-context/3/steps/48055