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Hospitalisation caused by Flu in patients aged 65 years and over

Analytics on hospital admissions caused by Flu after the annual Influenza immunisation period (October and November) in patients aged 65 years and over.

Influenza, or flu, is a viral infection that mainly affects the respiratory system and can cause mild illness in most people. It can cause severe illness and even death among vulnerable groups including older people, pregnant women and people with an underlying health condition.

In the UK the annual flu season runs from about October to March and most cases of flu occur between December and March. Studies have shown that vaccination can reduce the risk of flu related hospitalisation although, the effectiveness of the vaccine can vary year on year. The annual flu vaccination cycle runs mainly during October and November.

A lot of vulnerable adults spend considerable amount of time in hospital during the annual vaccination cycle and often miss their GP’s flu clinics. At present there is no provision to provide vaccination to patients admitted in hospitals.

In this report we look specifically at patients 65 years and over who were discharged from hospital during the annual vaccination period of October and November and got admitted on a later date with primary diagnosis of flu, 14 days after they were first discharged during that period. It usually takes 10 to 14 days for the flu vaccine to take effect. If there was a provision to vaccinate older people at time of discharge could it potentially reduce the number of admissions, improve hospital bed availability and most importantly could it potentially prevent deaths caused by flu?

Accessibility note

This tool is in Microsoft PowerBI which does not fully support all accessibility needs. If you need further assistance, please contact us for help.

How to use the report

The visuals in the ‘summary’ or front page of the report are meant to be read from left to right. The information displayed relates to patients who are 65 years and over who were discharged from hospital during the annual flu vaccination period of October to November, irrespective of the condition they were admitted for.

The bar chart on the left shows the number of patients discharged from hospital and were subsequently admitted 14 days after the discharge with a primary diagnosis of flu. For patients who have had more than one discharge during the annual flu vaccination period, only the first discharge is considered to avoid double counting the patient.

The chart in the middle shows number of admissions by month for patients admitted with a primary diagnosis of flu, 14 days after their earliest discharge during the annual flu vaccination period.

The funnel chart at the right shows the number of people that were discharged from hospital during the annual flu vaccination period who died, some with flu as cause of death.

On the right-hand side of the page there are two links which provide additional information related to this subject. The charts in the ‘Background information’ page displays the timeseries showing the growth in number of flu related deaths and hospitalisations which provides some context for this analysis. The tables and charts in the ‘Trust level information’ page of the report shows the same information broken down to Trust level. User can select a Trust and additionally see information for its top 10 peers as well.


The table lists the filters applied to HES Admitted Patient Care (APC) data.

HES APC data attribute Codes
DIAG_03_01 (3-character primary diagnosis)

J10 = Influenza due to identified seasonal influenza virus

J11 = Influenza, virus not identified
EPISTAT (Episode status) 3 = Finished episode
EPIORDER (Episode order) 1 = First episode in spell
STARTAGE (age at start of episode) Between 65 and 120
CLASSPAT (Patient classification)

1 = Ordinary admission

2 = Day case admission

Used to filter patients discharged during annual flu vaccination cycle who have had a subsequent admission with primary diagnosis of Flu

Notes and data sources

  1. All hospital data are sourced from Hospital Episodes Statistics (HES) Admitted Patient Care (APC) Commissioning Data Set.
  2. Published APC data for the period April 2017 to March 2018 has been used in this report to display information in the ‘Summary’ page related to discharges during vaccination period and subsequent admissions caused by flu.
  3. Published APC data for financial years 2008-09 to 2017-18 has been used to create the timeseries charts.
  4. ONS death registrations data for the period January 2000 to September 2018 that has been linked to HES has been used to display information on deaths caused by flu. This dataset is also known as the Linked HES-ONS mortality dataset. It is worth noting that not all persons in the ONS death registrations dataset will match to a patient in HES for one of the following reasons. Identifiable data for some patients are anonymised in HES for various reasons which prevents data linkage for those persons. Additionally, linkage will not happen where there are data quality issues such as missing or invalid identifiers or if the person does not have data in HES.


In accordance with HES disclosure control guidance all numbers between 1 and 7 have been rounded to 5, everything else has been rounded to the nearest five.

Last edited: 24 May 2021 3:20 pm