The reminder comes from NHS Sussex, which says 470,000 eligible residents across Sussex have not yet taken up the free vaccination, putting them at higher risk of serious illness or complications.
Dr Amy Disanayake, interim chief medical officer for NHS Sussex, said: “Flu levels continue to rise, and we are already seeing the impact across local health services.
“Those who are eligible for the free flu vaccination are offered it because they are more vulnerable to serious complications from flu, and it is important that they come forward as soon as possible.”
As of the latest data, 506,000 eligible individuals in Sussex have received the vaccine, covering just 52 per cent of those entitled to it.
Flu hospital admissions have risen in recent weeks, with health leaders warning that a new strain is contributing to increased illness.
Flu vaccinations are available through GP practices, community pharmacies, school teams for eligible children and walk-in services listed on the NHS Sussex website.
The flu virus spreads easily, especially during the early days of infection, and can survive on hands and surfaces for up to 24 hours.
The public is being reminded of basic hygiene measures to reduce transmission, including regular handwashing with warm water and soap, covering the mouth and nose when coughing or sneezing and staying home if unwell.