The COVID-19 pandemic affected the health of millions of people across the country -- at the time of publication, there have been over 20 million confirmed cases of the virus in England and just over 170,000 deaths within 28 days of a positive test, and the ONS estimate that 71% of the population have contracted the virus. Thinking about young people specifically, just over 1.3 million 15- to 19-year-olds are estimated to have had COVID-19 since February 2020. Long COVID -- defined as when an individual who suffered from a COVID-19 infection experienced symptoms more than 4 weeks after they first had the virus (which were not explained by something else) emerged as an additional risk from COVID-19 infection. This briefing explores the incidence of COVID-19 and long COVID among the authors' cohort, as well as how many young people were asked to shield during the pandemic, comparing patterns by socio-economic background. It considers how this has affected young people's education, including GCSE attainment using linked National Pupil Database (NPD) data. Aside from COVID-19 directly, the brief also investigates patterns in exercise, smoking, alcohol and drug use among young people. Compared to cohorts of young people before the pandemic, previous research has found smoking and drug use appears to be declining, whilst e-cigarette use is increasing, with cigarette, alcohol and drug use more common for those who had more social interactions outside of school and the home during the pandemic. Existing research suggests participation in sport and exercise during the pandemic also declined, particularly for those from deprived backgrounds, who had less access to outside space. Parent and guardian responses are also analysed relating to their health behaviours, as well as their behaviour in relation to self-isolation and COVID-19 vaccination. [For the fourth brief, "Mental Health and Wellbeing," see ED625716.]