BackgroundIn the UK, there have been multiple waves of COVID-19, with a five-tier alert system created to describe the transmission rate and appropriate restrictions. While acute mortality decreased, there continued to be a significant morbidity, with individuals suffering from persistent, life-restricting symptoms for months to years afterwards. A remote rehabilitation tool was created at the Defence Medical Rehabilitation Centre (DMRC) Stanford Hall to assess post-COVID-19 symptoms and their impact on the UK military.This study aims to understand changes in post-COVID-19 syndrome between wave 1 and wave 2, identify interactions between alert level and symptoms and investigate any predictive nature of acute symptoms for postacute symptomology in a young, physically active population.MethodsCross-sectional study of 458 consecutive remote rehabilitation assessments performed at DMRC Stanford Hall between 2 April 2020 and 29 July 2021. Consultations were coded, anonymised, and statistical analysis was performed to determine associations between acute and postacute symptoms, and between symptoms, alert levels and waves.Results435 assessments were eligible; 174 in wave 1 and 261 in wave 2. Post-COVID-19 syndrome prevalence reduced from 43% to 2% between the waves. Acutely, widespread pain was more prevalent in wave 2 (p<0.001). Postacutely, there was increased anxiety (p=0.10) in wave 1 and increased sleep disturbance (p<0.001), memory/concentration issues (p<0.001) and shortness of breath/cough (p=0.017) in wave 2. Increasing alert level was associated with increased postacute symptom prevalence (p=0.046), with sleep disturbance increasing at higher alert level (p=0.016). Acute symptoms, including fatigue, sleep disturbance and myalgia, were associated with multiple postacute symptoms.ConclusionsThis study reports the overall prevalence and symptom burden in the UK military in the first two waves of COVID-19. By reporting differences in COVID-19 in different waves and alert level, this study highlights the importance of careful assessment and contextual understanding of acute and postacute illnesses for individual management plans.