To create case definitions for confirmed COVID-19 diagnoses, COVID-19 vaccination status and three separate definitions of high risk of severe COVID-19, as well as to assess whether the implementation of these definitions in a cohort reflected the sociodemographic and clinical characteristics of COVID-19 epidemiology in England.

Retrospective cohort study.

Electronic healthcare records from primary care (Clinical Practice Research Datalink, CPRD) linked to secondary care data (Hospital Episode Statistics) data covering 24% of the population in England.

2 271 072 persons aged 1 year and older diagnosed with COVID-19 in CPRD Aurum between 1 August 2020 and 31 January 2022.

Age, sex and regional distribution of COVID-19 cases and COVID-19 vaccine doses received prior to diagnosis were assessed separately for the cohorts of cases identified in primary care and those hospitalised for COVID-19 (primary diagnosis code of ICD-10 U07.1 ‘COVID-19’). Smoking status, body mass index and Charlson Comorbidity Index were compared for the two cohorts, as well as for three separate definitions of high risk of severe disease used in the UK (National Health Service Highest Risk, PANORAMIC trial eligibility, UK Health Security Agency Clinical Risk prioritisation for vaccination).

Compared with national estimates, CPRD case estimates under-represented older adults in both the primary care (age 65–84: 6% in CPRD vs 9% nationally) and hospitalised (31% vs 40%) cohorts, and over-represented people living in regions with the highest median wealth areas of England (20% primary care and 20% hospital admitted cases in South East vs 15% nationally). The majority of non-hospitalised cases and all hospitalised cases had not completed primary series vaccination. In primary care, persons meeting high-risk definitions were older, more often smokers, overweight or obese, and had higher Charlson Comorbidity Index score.

CPRD primary care data are a robust real-world data source and can be used for some COVID-19 research questions, however, limitations of the data availability should be carefully considered. Included in this publication are supplemental files for a total of over 28 000 codes to define each of three definitions of high risk of severe disease.

Preterm birth is a leading cause of perinatal morbidity and mortality. During the COVID-19 pandemic, reduction in rates of preterm birth in women exposed to viral mitigation measures was reported by multiple studies. In addition, others and we observed a more pronounced reduction of preterm birth in women who had previously experienced a preterm birth. The aim of this pilot study is to establish the feasibility of a lifestyle intervention based on viral mitigation measures in high-risk pregnancies, with the ultimate aim to reduce the incidence of preterm birth.

One hundred pregnant women, enrolled in antenatal clinics at two tertiary maternity centres in Melbourne, Australia, who have had a previous preterm birth between 22 and 34 weeks gestation will be recruited. This is a two-arm, parallel group, open-label randomised controlled feasibility trial: 50 women will be randomised to the intervention group, where they will be requested to comply with a set of lifestyle changes (similar to the viral mitigation measures observed during the pandemic). Another 50 women will be randomised to the control group, where they will undergo standard pregnancy care. The primary outcome of this trial is feasibility, which will be assessed by measuring patient eligibility rate, recruitment rate, compliance rate and data completion rate. Secondary outcomes include incidence of preterm birth, maternal satisfaction, maternal quality of life and other pregnancy outcomes. Standard methods in statistical analysis for randomised controlled trials on an intention to treat basis will be followed.

This trial has been approved by the Monash Human Research Ethics Committee; approval reference number RES-22-0000-122A. Study findings will be reported and submitted to peer-reviewed journals for publication, and presentation at conferences.

ACTRN12622000753752; Pre-results.