Influenza is a seasonal respiratory virus of significant public health importance. Each year an estimated 3 to 5 million cases of severe influenza illness occur globally, and between 250,000 and 500,000 people will die as a result of their infection. The young, the elderly, pregnant women and people with underlying medical conditions are at particular risk of severe infection. This study seeks to estimate the annual risk of hospital admission for influenza in patients registered with general practices in England. No formal testing will be undertaken.
This study seeks to generate counts of patients admitted to hospital with influenza in England between 2000 and 2017. Counts will be split further by broad age groups (<18, 18-64 & 65+ years), the primary nature of the hospital admissions (e.g. flu was recorded as the primary reason for hospital admission), the incident nature of the hospital admissions (e.g. if a patients had previous admissions in the 90 days prior to each admission) and whether the admission occurred in flu seasons (nominally week 40 of one year to week 15 of the next) or not. The study will use a CPRD source population to form the denominator on which risk estimates will be calculated. No formal testing will be undertaken.
Health Outcomes to be Measured:
Flu hospital admission, as defined by a record of an ICD-10 admission code for influenza (J09*, J10*, J11*)