Objective To determine the effect of population level implementation of a test-and-treat
approach to correction of suboptimal vitamin D status (25-hydroxyvitamin D (25 (OH) D)< 75 …

Vitamin D deficiency has been reported to associate with the impaired development of
antigen-specific responses following vaccination. We aimed to determine whether vitamin D …

Background Long COVID is a well recognised, if heterogeneous, entity. Acute respiratory
infections (ARIs) due to other pathogens may cause long-term symptoms, but few studies …

Background The risk factors for recovery from COVID-19 dyspnoea are poorly understood.
We investigated determinants of recovery from dyspnoea in adults with COVID-19 and …

Background Older age is associated with poorer outcomes to COVID-19 infection. The
Norwegian Institute of Public Health established a longitudinal cohort of adults aged 65–80 …

Background Long COVID is a major problem affecting patient health, the health service, and
the workforce. To optimise the design of future interventions against COVID-19, and to better …

Introduction Cohort studies generate and collect longitudinal data for a variety of research
purposes. Randomised controlled trials (RCTs) increasingly use cohort studies as data …

Background The imposition of restrictions on social mixing early in the COVID-19 pandemic
was followed by a reduction in asthma exacerbations in multiple settings internationally …

Background The association between air quality and risk of SARS-CoV-2 infection is poorly
understood. We investigated this association using serological individual-level data …

Background Studies into the bidirectional relationship between sleep and long COVID have
been limited by retrospective pre-infection sleep data and infrequent post-infection follow …