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Influenza (commonly known as flu) is highly infectious and causes acute viral infection of the respiratory tract. This virus is spread through droplets, aerosol or direct contact with respiratory secretions from an infected individual. The usual incubation period is one to three days.
For healthy individuals, influenza is unpleasant but usually self-limiting with recovery between two to seven days. Some people are at increased risk of it causing severe illness or even death. Complications of influenza can include:
Those at greatest risk of serious illness from influenza include:
Most influenza vaccines available in the UK are inactivated with the exception of the live attenuated influenza vaccine (LAIV) – this is the vaccine given to most eligible children. The brand name for LAIV available in the UK is Fluenz®. LAIV contains live viruses that have been attenuated (weakened) and cold adapted so that they can only replicate in the lower temperatures of the nasal passages.
Because of the changing nature of influenza viruses, and changes in the strains circulating and causing disease, the World Health Organization (WHO) monitors the epidemiology of the influenza viruses throughout the world and makes annual recommendations about which strains should be included for the upcoming winter.
Read the World Health Organization (WHO) Recommended composition of influenza virus vaccines for use in the 2025-2026 northern hemisphere influenza season (who.int) (external site).
There are a number of inactivated influenza vaccines available. You can find out more about each vaccine in the summary of product characteristics (SmPC) which can be found at the electronic medicines compendium (emc) link below by entering the vaccine name:
The SmPC for LAIV is available at:
Vaccination programme recommendations from the Joint Committee on Vaccination and Immunisation (JCVI) and Welsh Government policy can be found at the links below.
Joint Committee on Vaccination and Immunisation - GOV.UK (external site) (read JCVI publications and statements; search e.g. influenza)
This eLearning module is suitable for all healthcare professionals, including health care support workers who immunise against flu or provide flu immunisation advice. It is the clinical update for Wales and has been updated for the 2025-26 flu season. This module is available on ESR and the Learning@Wales platform. More information on how to access module is available on our flu clinical update for Wales 2025-26.
The module explains why the annual flu vaccine is so important for all health and social care workers. It gives an overview of flu and its complications. It gives details of who is eligible to receive the vaccine and how to obtain it. It is suitable for all NHS Wales workers, non-NHS health care workers, people who work in care homes, social care and the third/voluntary sector. More information on how to access module is available here: Flu vaccine information for health and social care staff in Wales 2025-26 - Public Health Wales. This module is not a clinical update.
Further information about these modules and how to access them is available here: Immunisation eLearning - Public Health Wales (nhs.wales)
Further vaccination training information and resources are provided on the Training Resources and Events page.
Keep in mind that vaccine eligibility information in Wales and England differs.
PGD templates for the influenza vaccine can be accessed from Patient Group Directions (PGD) - Welsh Medicines Advice Service (wales.nhs.uk) (external site).
Flu surveillance information, including vaccine uptake, can be seen at Public Health Wales: Weekly influenza and acute respiratory infection report.
A ‘speedometer’ can be used to demonstrate flu vaccine uptake data. For health and social care professionals who would like to create their own speedometer for vaccine uptake, here is a template containing instructions.