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Influenza weekly overall hospital admission rate

Last updated on Tuesday, 3 September 2024 at 09:23am

Summary

Topic
Influenza
Category
headline
API name
influenza_headline_hospitalAdmissionRateLatest

Rationale

Seasonal influenza occurs every year and is a key driver for winter pressure on the NHS. The impact of influenza on the NHS depends on several factors:

  • which strains of the virus are circulating
  • Age (under 5 years and over 65 years) and underlying illness
  • how effective the annual vaccine is
  • how many people are immunised in the target groups for influenza immunisation

Understanding rates and patterns of hospital admissions can help to inform planning around hospital pressures including beds, staffing and public health messaging on immunisation.

Definition

This metric shows the rate per 100,000 people of newly confirmed influenza hospital admissions in the last 7 days to any level of care inclusive of Intensive Care Unit (ICU) and High Dependency Unit (HDU) .

Methodology

Updates from SARI Watch are published in the UKHSA National Influenza and COVID-19 Surveillance Report on a Thursday during influenza season and contains data up to the previous Sunday.

This metric shows the rate per 100,000 people in the NHS trust catchment population who were admitted to hospital with test-confirmed influenza in the last 7 days. A positive result from molecular Point of Care tests, polymerase chain reaction (PCR) and antigen tests are acceptable for case confirmation. The rate is calculated by counting the number of influenza-related hospital admissions in the latest 7 days, dividing by the catchment population of the participating NHS trusts and then multiplying by 100,000.

Hospital provider trusts do not have geographically defined boundaries for their client population nor do they have all encompassing lists of registered patients. The Office for Health Improvement and Disparities has adopted a proportionate flow method to calculate catchment populations. Using this method, Hospital Episode Statistics Admitted Patient Care (HES APC) data was used to count the number of patients admitted to hospital from every small geographical area in England (based on Middle layer Super Output Area (MSOA)).

For each MSOA, the number of patients admitted to each hospital trust was calculated as a proportion of all patients from that MSOA admitted to hospital. This proportion was then applied to the resident population of each MSOA and the resulting population counts added to give an overall hospital catchment population. The catchment year applies to the year of mid-year population estimates used to calculate the population.

Caveats

The data comes from a sentinel network of participating trusts. This is data submitted voluntarily by a small subset of acute NHS trusts (in previous seasons this has ranged from 25 to 30 trusts and may be similar future seasons) . As a sentinel surveillance system there may be some geographic under representation as well as variation among trusts reporting from week to week. Hence the most recent weeks of surveillance tend to be subject to retrospective changes as trusts submit delayed reports. Also, the most recent weeks of surveillance may be updated as trusts submit delayed reports.

However, despite these caveats, the data provides an indication of the progress and intensity of influenza during the course of the season and contributes to an overall epidemiological picture of influenza along with other surveillance indicators operating in the winter period.

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