Many people who are at risk of becoming seriously ill if they catch flu have not yet been vaccinated against it.
The number of pensioners who have received the vaccination has fallen compared to last year.
And the number of other "at risk" patients, who are under the age of 65 and suffer from various medical complications, has also decreased.
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Michael Fallon has received reassurances from his US counterpart that security ties with Britain will "endure" following a vote for Brexit.
On Friday, police said it appeared the girl had shot herself in the face with the weapon.
The showers will be slow-moving, heavy and thundery at times, particularly in central and eastern areas.