Our next scheduled release is in the New Year 🎉. Until then, the IDM team has earned some festive downtime. 🧵8/8

This has been a Herculean effort by the Infectious Disease Modelling Team. Myself, Jon Mellor, Martyn Fyles,Tom Ward and Chris Overton worked on it around the clock to get this done. 🧵7/8

Our survey sample isn’t perfectly representative of the English and Scottish population. We used population estimates from nations, regions, age groups and sexes (supplied by the @ONS) to re-weight the estimated prevalence to be more representative. 🧵6/8

LFD tests are less sensitive, particularly towards the end of infections. This means we have to account for lower sensitivity to convert positivity to prevalence. We developed a model that uses data from the repeat tests to work out how sensitive the LFD tests are 🧵5/8

The ONS previously used PCR tests. These tests rarely return a false negative result (high sensitivity). This meant the reported positivity (the proportion of positive PCR tests) was close to prevalence (the proportion of the population who were infected) 🧵4/8

Around 150,000 participants have been recruited. Participants are sent lateral flow device (LFD) tests and self report results through an online questionnaire. After someone tests positive, they keep doing tests every other day until they get two negative results in a row 🧵3/8

The headline is that prevalence in 🏴󠁧󠁢󠁥󠁮󠁧󠁿 and 🏴󠁧󠁢󠁳󠁣󠁴󠁿 was 4.2% on the 13th of December. This represents an increase over the past two weeks and is equivalent to around 1 in 24 people being infected. Prevalence is higher in those aged 18-44 compared to those aged 65 or over🧵2/8