Flu vaccine stocks are running low as thousands of people hurry to protect themselves against the virus.
Dozens of private clinics, pharmacies and high street chains in Sussex have reported that they have sold out of the jab.
The vaccine protects against three different types of flu, including swine flu.
The NHS is offering free jabs to over 65s, pregnant women and people with long term health problems such as heart disease, diabetes or asthma.
Take-up rates across the county have risen to around 70% for pensioners but only half of at risk under 65s have accepted the offer.
However swine flu has more of a serious effect on younger people, leading to scores of patients not eligible for a free vaccine opting to pay for it instead.
NHS chiefs have admitted offering free single swine flu vaccinations left over from a year ago to at-risk patients in some areas because of a shortage.
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