Contacts in context: large-scale setting-specific social mixing matrices from the BBC Pandemic project

Petra Klepac; Adam J Kucharski; Andrew JK Conlan; Stephen Kissler; Maria Tang; Hannah Fry; Julia R Gog

We follow [29] to infer mixing matrices from the self-reported contact data. We group the study participants and their contacts by age into following age groups: 0-4, 5-9, 10-12, 13-14, 15-17, 18-19, 20-21, 22-24, then 5 year age bands from 25 to 74, with a single category for those aged 75 and over: the finer structure chosen to provide higher resolution for school and university ages. For each of those age groups, we find t ij : the total number of reported contacts over the course of 24 hours between participants in age group j and their reported contacts of estimated age group i. To find the mean number of contacts (m ij ) who are in age group i as reported by participants in age group j we divide t ij by n j -the total number of participants in age group j. This results 2 in the 'social contact matrix' M = (m ij ), where m ij = t ij /n j . This is the raw contact matrix as derived from our study data.